Maps of Sligo and Leitrim, Ireland


These River Basin Districts are further sub-divided into 40 Hydrometric Areas of which the following ones are in the Sligo / Leitrim region :

26 = Upper Shannon (with Boyle system)

Sub-catchments as in Lough Derg & Lough Ree report :

Shannon (at Roosky) i.e. everything upstream incl. Boyle R.

River Rinn

34 = Moy (and Killala Bay)

35 = Ballysadare and minor catchments of Sligo (Sligo Bay and Drowse)

36 = Erne (with Lough Macnean)

One of the basic pieces of data being collected are the records of water level.  Up until 2001 this was done at fixed stations using Autographic Water Level Recorders but these have been replaced by Data Loggers that digitally record the water level at 15 minute intervals using a float and counterweight system.  The stations are operated by County Council staff and the data are analysed centrally by the Environmental Protection Agency (see  Apparently there are about 12 such fixed stations in this geographical area.

Inland Fisheries Ireland (previously Central and Regional Fisheries Boards)

Fisheries resources were managed by regional boards for many years.  Three Fisheries Boards included parts of either County Sligo or Leitrim within their areas which were :

North-Western Regional Fisheries Board

Northern Regional Fisheries Board (Lough Melvin)

Shannon Regional Fisheries Board (Lough Gara, Shannon)

and these were managed and assisted by the Central Fisheries Board.

All this changed in 2010 with the abolition of the Central and Regional Fisheries Boards and a more centralised management of the fisheries resource through Inland Fisheries Ireland (IFI).  The management of river and lake fisheries however did not change to any great extent as the river catchments were always the basis of the management areas.  This makes complete sense as river catchments are usually the best way to manage the environment!  The result is that most of Sligo and much of the northern half of Leitrim falls within the Western River Basin District (Grange River, Drumcliff River, Garavogue River, Ballysadare River and River Moy - green on map); a small area of Sligo and parts of eastern Leitrim fall within the North Western River Basin District Duff, Drowes including Lough Melvin and the Erne - orange on map); and most of south Leitrim and bits of south Sligo are in the catchment of the River Shannon including Lough Gara Lough Allen etc. - brown on map).

International Council for the Exploration of the Sea (ICES)  regions

The ’Marine Census Areas’ system of dividing up the seas around Ireland and Great Britain was popular in the 1970’s and 1980’s but seems to have been replaced by the more internationally based ICES Regions.  These are much larger units and are not as informative as the older system when it comes to local patterns of distribution as can be seen from the maps shown below.

European Terrestrial Reference System (ETRS89).

With the advent of satellite communications there is no longer such a need for triangulation, leveling and benchmarking and these methods are rapidly becoming historical curiosities.  Global Positioning Systems (GPS) allow any Irish user to identify their position to a precision of a few millimetres using the European Terrestrial Reference System (ETRS89) as the reference frame.  Quality GPS equipment tied in with the ETRS89 can be approximately 10x more precise than the ground-based triangulation system upon which the Irish Grid was founded.  The difference between the two systems is often of the order of 55 meters (Cory et al. 2001) and it is not possible to make GPS coordinates fit onto existing Irish Grid maps.

Irish Transverse Mercator (ITM) grid.

A new grid was proposed by Corry et al. (2001) which they called the Irish Transverse Mercator (ITM).  This is in the process of being adopted by the Ordnance Survey of Ireland (OSI) and the Ordnance Survey of Northern Ireland (OSNI).  This grid is centered on the 8o longitude meridian as is the Irish Grid.  This meridian goes right through the middle of Leitrim (see map in section on Geographical Position).  The adoption of this system will mean that all 1:50,000 maps will have to be republished with the adjusted grid (and all old maps will be redundant for grid references).  It will also mean that all grid references taken using the Irish Grid that are held on databases or are published will have to be re-calculated. The new ITM grid will also be entirely digital and will be the distance in meters east (6 figures) and north (another 6 figures) from a defined point (the false origin) off the south-west of Ireland.  Results using a GPS will exactly agree with the position on the new OSI/OSNI sheets (that is assuming the GPS is of a model with ITM programmed in!).  For further information see :

Universal Transverse Mercator (UTM) grid.

This grid converges towards the North Pole and thus the eastings are not parallel.  The result is that grid areas within this grid system can be trapeziums or triangles.  A 50 km UTM grid has sometimes been used to map the distribution of species across the whole of western Europe.

Universal Transverse Mercator grid

Tetrads within a hectad

2 x 2 km squares within 10 x 10 km squares

Meteorological Sea Areas

Meteorologists work on a very large scale so that the entire marine region of Sligo and Leitrim lies in sea area Malin which also includes the northern coastline of Ireland from Erris Head on Belmullet Co.Mayo right around to Belfast Lough in Co.Down and even encompassing parts of the west coast of Scotland.  Nominally, inland areas are also influenced by waether in this sea area which also takes in the southern extremities of Sligo and Leitrim.  Weather forecasts for the Sligo and Leitrim coast are best represented by reports from Erris Head in Mayo and Rossaun Point in Donegal.



In the nineteenth century the island of Great Britain was divided into 112 vice-counties by Watson (1852) for the purpose of recording the distributions of biological (mainly botanical) organisms.  This system was adopted in Ireland when Praeger (1896) sub-divided the country into 40 vice-counties and designated County Sligo as H.28 and County Leitrim as H.29, 'H' standing for Hibernia to distinguish the numbering system from that of Great Britain.  This system is still used in the 21st century but with better maps and the computerisation of data the vice-county system is gradually falling out of favour.

Hectads (‘dot maps’) & tetrads

Since the 1970's naturalists have mainly used the Irish grid as a means of recording the distribution of plants and animals and in particular the grid lines at 10 km spacing that define squares of 10 x 10 km (enclosing an area of 100 square kilometers) and now called hectads, have found to be suitable for most recording purposes.  Production of 'dot' maps. 10km squares (hectads) are used as biological recording units.

A famous geographer, Dudley Stamp, once said that “nature abhors straight lines and undoubtedly detests kilometre grids”.  He was almost certainly correct in his assertion and dot maps should be interpreted with great caution!

BSBI grid

In 1954 the Botanical Society of the British Isles planned to map every species of the flora of Great Britain and Ireland.  The British National Grid was printed on maps of Great Britain at the time but no such grid was available for Irish maps.  In fact there was a ‘Military Grid’ in existence and an Irish Grid was being planned, based upon this.  Professor David Webb arrived at a solution to the problem by simply extending the British National Grid lines westwards to cover the whole of Ireland and he produced a set of maps with grid lines at 10 km spacing.  When the 'Atlas of the British Flora' (Perring & Walters 1962) was completed maps showing the BSBI grid were published for each species of vascular plant.  It was technically wrong to extend the British National Grid westwards due to parallax error and this BSBI grid was discontinued once a National Irish Grid became widely available on maps.

The boundary of County Sligo was redrawn for administrative reasons under the Local Government Act, 1898 and 7 townlands (comprising 1,917 acres) in the parish of Castleconor in the western most part of the county near Ballina, were annexed to Mayo.  This change came about after Praeger had defined his vice-counties and by convention the vice-county boundaries follow the path of the old administrative county boundaries (see map and paper by Webb 1980) .  Occasionally this leads to some confusion for those involved in biological recording.  Unfortunately, the area affected by the change in Sligo/Mayo boundary runs right beside Moyview where the ornithologist Robert Warren once lived.


Andrews, J.H. (1997)  Shapes of Ireland.  Maps and Their Makers 1564-1839. Geography Publications, Dublin.

Cory, M.; R. Morgan, C. Bray & I. Greenway (2001)  Session 8 - Reference Frame in Practice.  A new coordinate system for Ireland.  ‘New Technology for a New Century’ International Conference of Fédération Internationale des Geométrès, Seoul, Korea.

Cotton, D. & R. Thorn (1993)  Reviews of maps.  Ordnance Survey of Ireland 1:50,000, 1st [The Rambler] Series, Preliminary Edition, Sheet 16, Benbulbin.  Dublin: Ordnance Survey of Ireland, 1992.    Irish Geography 25(2):202-203.

County Sligo Heritage and Genealogy Society (2003)  County Sligo in 1837.  A Topographical Dictionary by Samuel Lewis.  The County Sligo Heritage and Genealogy Society, Sligo. (see also Lewis 1837 shown below).

Durand, S. (2000)  Drumcliffe.  The Church of Ireland Parish in its North Sligo Setting.  Drumlin Publications, Manorhamilton.  (Includes a map of “Drumcliff Parish and Surrounds”).

Heppell, D. (1964)  The British Marine Census Areas.  Journal of Conchology 25:299-303.

Horner, A. (2011)  Mapping Sligo in the early nineteenth century; with an atlas of William Larkin’s map of County Sligo, 1819.  Wordwell Books, Dublin.

Irish National Committee for Geography (1979)  Atlas of Ireland. Royal Irish Academy, Dublin.

Lewis, S. (1837)  Atlas of Ireland.  S. Lewis & Co., London or Creighton, R. (1837)  Maps of Counties Sligo and Leitrim in Haydn, Joseph (1837)(ed.)  A Topographical Dictionary of Ireland; with an accompanying Atlas and an appendix describing the Electoral Boundaries of the several Boroughs.  Samuel Lewis, London.  (Known as Lewis' Topographical Dictionary).

Moody, T.W. & F.X. Martin (1967)  The Course of Irish History.  The Mercier Press, Cork. (Page 24 mentions mapping and Figure 20 is a map of “Ireland in the 8th century” by F.J. Byrne).

National Library of Ireland (1980)  Ireland from Maps. National Library of Ireland, Dublin.

Praeger, R.L. (1896)  On the botanical subdivision of Ireland.  Irish Naturalist 5:29-38.

Swift, M. (1999)  Historical Maps of Ireland.  Parkgate Books, London.

Verschoyle, Archdeacon (1838)  Notices on the geology of the north coast of the counties of Mayo and Sligo in Ireland.  Transactions of the Geological Society of London (2nd Series) 5(11):149-170 (with 1 map).  (1832 N.S. 5 from card index of National Library of Ireland).

Watson, H.C. (1852)  Cybele Britannica (3rd volume)


William Larkin published an atlas of six engraved sheets that when laid out together reveal a map of County Sligo that is 1.8 m x 1.7 m in size and shows a great deal of detail.  It is reproduced in Horner (2011).


Alexander Nimmo prepared a map of Sligo Harbour and approaches with soundings for the Commissioners of Sligo Port.  This map includes detailed instructions for ships entering the harbour and was published for the use of the Irish Fisheries as well as to help plan for proposed improvements.  It is reproduced in Swift (1999).


Northern coast of Mayo and Sligo by Archdeacon Verschoyle is a coloured sheet, 25.5 cm x 53 cm (Verschoyle 1832 or 1838?).


Creighton, R. (1837)  Maps of Counties Sligo and Leitrim in Haydn, Joseph (1837)(ed.)  A Topographical Dictionary of Ireland; with an accompanying Atlas and an appendix describing the Electoral Boundaries of the several Boroughs.  Samuel Lewis, London.  (Known as Lewis' Topographical Dictionary).  There was a second edition in 1842.  The maps were reprinted by Kennys Bookshops and Art Galleries Ltd., Galway in the 1990's.

Tetrads from which the brimstone moth has been recorded

Map of Counties Sligo & Leitrim overlain by 10 km square (hectad) grid





Map of Ireland with 100 km squares overlain


A miniature set under the title "A Geographical Description of the Kingdom of Ireland" was published by Francis Lamb with Robert Morden and William Berry.  This was re-issued in 1689 and 1695.

In the National Library of Ireland there is an early miniature edition as Petty, Sir William. "A Geographical Description of ye Kingdom of Ireland.  Collected from ye actual survey made by Sr William Petty.  Corrected and amended, by the advice, & assistance, of several Able Artists, late Inhabitants of that Kingdom"  Boundaries in this edition are tinted in yellow, pink and green.


Most of the original maps of Petty were destroyed in a fire.


Small-scale editions were published by John Bowler (1720 & 1732) who re-engraved some of the maps and added roads.

In the National Library of Ireland there is an edition of 1728 measuring 17.5 x 13.5 cm under the reference number of J9120941 and from the Joly collection.

"A Geographical Description of the Kingdom of Ireland newly corrected and improved by actual observations.  The whole being laid down from the best maps viz : Sir Wm. Petty's Mr Pratt's etc."

This edition has short introductory remarks that describe the counties and their principal towns.

There are 3 or 4 other editions of miniatures in the National Library of Ireland under the same reference number or under the reference number of LO

The Royal Irish Academy has a map by Petty showing the Baronies under reference number 23 L 42.

More of the maps were lost in 1922 when the Public Record Office was destroyed in the rising.  However, many of the originals had copies made of them and most of these copies survive.  e.g.

The parish maps of the Down Survey for the County of Leitrim by Wm Petty (1655-59) copied by Daniel O'Brien (1786-87) is a set of 25 Ms maps with accompanying terriers and copy of attestation by William Petty and Wm. Gorkin at beginning of volume.  Dated 1659.  National Library of Ireland Ms 717.  Pos 7383.




'A prospect of Sligo' by Thomas Phillips.  Pencil, pen and ink wash, slight colour.  36cm x 92cm.  From card index of National Library of Ireland.  Ms 3137 (35).


Map of 'Counties of Sligo and Mayo' by Herman Moll at a scale of 2.5" to 25 miles (8" x 6.5").  Original in TCD Language and Comm Studies; copy in Sligo County Library.


'Map of County Sligo showing baronies in colour' by Scale (1798 edition).  In Sligo County Library.


Sketch of the County of Leitrim 23cm x 18cm.  4 Irish miles to 1 inch.  In McParlan (1802)  Statistical Survey of the County Leitrim. From card index of National Library of Ireland.  Ir 3141.


Grierson - barony map in county library

Maps offer one of the most valuable means of summarising environmental information.  For generations people have drawn two dimensional maps, often lavishly illustrating them to create an art form.  With the advent of more powerful computers becoming widely available, three-dimensional maps and maps made up of layers (Geographic Information Systems), have become commonly used in all kinds of spatial analysis.  This section is a brief history of maps and mapping in Ireland with special attention being given to the coverage of counties Sligo and Leitrim.  In particular, maps of relevance to the natural environment are highlighted.

Useful sources of information on Irish maps are Irish National Committee for Geography (1979) for an atlas showing a wide selection of maps; the National Library of Ireland (1980) gives a limited selection of historical maps; Andrews (1997) for information between the years 1564 and 1839; and Swift (1999) for the history of Irish maps (see the list of references at bottom of this page).



Claudius Ptolemaeus (Ptolomy from Greece) included Ivernia (Hibernia, Ireland) along with Albion (Great Britain) on his map as a part of the Pretanic Islands (British Isles).  The place named Nagnatai ‘habitation on the sea’ is positioned around where Sligo town is today.   Apparently Drumcliff was possibly larger than Sligo town in those days and this may be the place named Nagnatai.  However, the map is so unreliable that it may equally refer to the settlement of Galway so ownership of that name is disputed!


A map printed from a woodcut by Waldseemüller appears to jump from Donegal to Clew Bay without any mention of Sligo.  There is an island marked ‘iaroncl’ that is ascribed to ‘an island off Donegal’ (National Library of Ireland 1980).  This island is of the same shape and is in the correct geographical area for Inishmurray.  Given the importance of Inishmurray as an ecclesiastical site this may be the island shown on the map.


For the first time, Slego (Sligo) appeared on an Irish map that was first published in 1570 by Gerardus Mercator of Flanders (now in Belgium).  Mercator is not known to have visited Ireland and so would have relied upon other cartographers to provide the information and it is believed that this map was drawn by an English person about 1564.  Mercator’s Atlas of Europe depicts Ireland on pages 17 and 18.  Place names in the geographical area between Moynom (Moy River) and Dunbrofe (Bun Drowes river) include the Baye of Slego, L Gyll, New caftell (New Castle where Sligo town is today), and names the lands as occupied by “O : Conner Slego”.  Interestingly there is no indentation in the coastline between Mayo and Donegal to indicate Donegal Bay.  Presentation of this map is with west at the top of the page.



Strafford Survey of Connaught made by Thomas Raven in preparation for the planned plantation of the province.  His mapping effort included Sligo but not Leitrim.


Down Survey begun under direction of the Surveyor-General Benjamin Worsley, but was slow to get going.  This was done in order to share out the 'spoils' of lands confiscated by Cromwell's soldiers.


Civil Survey was done but it was not accurate and not fit for purpose.


Sir William Petty was given the task of co-ordinating what became known as the Down Survey. This was surveyed with a high level of accuracy using a chain survey method which was ‘laid down’ hence the name ‘Down Survey’.  The scale of the maps produced were very close to 1:50,000 which is comparable to the scale on the current Ordnance Survey Discovery Series.  Survey maps included a sheet for the whole of Ireland (A General Mapp of Ireland) and for each County, Barony and for many Parishes.

William Petty (1623-1687) was born in Hampshire and in 1652 was the Physician-General to the Army in Ireland when commissioned to assist Worsley, but the two men did not get on.  This survey was countrywide using 1000 men and incorporated the information from the Strafford Survey.  It was completed in just 4 years in 1657; maps engraved in Amsterdam in 1673; published in 1685; re-issued in 1690.  The maps are very basic with townland names, acreages and boundaries and the names of the former land owners before the land was confiscated.


Petrie "A Tour of Sligo" in Royal Irish Academy.

International Council for the Exploration of the Sea (ICES) map of the area around the west of Ireland

Down Survey map of County Sligo (1655)


Hiberniae Delinatio (Atlas of Ireland) was published (William Petty 1685)  Includes 'A General Mapp of Ireland' maps of the four provinces and county maps with barony boundaries.

There is also an engraving of Petty dated 1683 in the fronticepiece.

[In 1968 a limited edition of 500 copies of Atlas of Ireland was republished by Frank Graham, Newcastle-upon-Tyne.]

‘A General Mapp of Ireland’ by William Petty 1685, with detail of Sligo & Leitrim area


River Basin Districts & Hydrometric Areas (RBD)

The Republic of Ireland was divided up into 8 Water Resource Regions by the Environmental Protection Agency as a means to manage this important resource but with the need to comply with the EU Water Framework Directive (WFD) which came into force in December 2000.  These have been re-defined with boundary modifications as seven River Basin Districts.  Three of these districts include parts of Sligo or Leitrim :

Western River Basin District includes most of Sligo and western Leitrim as well as much of Mayo and Galway and a little piece of Clare.

Shannon River Basin District has a considerable part of Leitrim including Lough Allen and two small parts of Sligo including Lough Gara.

North-Western River Basin District includes the Drowes River and Lough Melvin and that part of the Erne catchment which is in the Republic of Ireland.

Archaeological Sites and Monuments Record (SMR)

Archaeology is not a part of natural history but very often the same environmental issues that affect wildlife sites are also of relevance to archaeology.  Sometimes the two disciplines come into conflict but more often they are cooperating in resolving issues.  A register and series of maps called the ‘Sites and Monuments Register (SMR)’ is a record of all known archaeological remains.  In County Sligo the register shows that this area has one of the highest densities of archaeological sites of any Irish county.  Ringforts comprise over one-quarter of the sites in the county and there are 150 crannógs.

                             Ringforts        1,700    26%

                             Crannógs          150       2.3%

                             Total sites      6,500      100%

County Council engineering areas

Work done on roads and other infrastructure in County Sligo is coordinated by an overseer  for each engineering area within the county.  Cooperation on issues such as  stranded whales and dolphins or bat roosts under bridges are just two ways in which the wildlife interests of the county may draw upon communication between the County Council and naturalists.  There are five engineering areas each with an overseer :




West Sligo


John The Map

John Callanan has used his own unique methods for mapping places around the world but he originates from Sligo and has produced a map of the county as well as towns within Sligo including Mullaghmore, Grange, Rosses Point, Strandhill, Sligo town, Ballysadare, Collooney, Riverstown, Ballymote, Bellaghy/Charlestown and Inishcrone.  In County Leitrim he has mapped Lurganboy, Manorhamilton, Dromahair, Drumshanbo, Ballinamore, Carrick-on-Shannon and Mohill.  It is well worthwhile visiting his web site at :

State Forestry : Coillte Forestry Business Area Units (BAU’s)

Forestry is a very important component of the ecological environment of Counties Sligo and Leitrim because it occupies over 10% of these counties.  State forestry is managed by Coillte who have an operating structure that since 01 October 2012 comprises of 8 management areas termed ‘Business Area Units‘   [prior to this there were 13 ‘Districts’]

The Sligo - Leitrim area is fragmented and falls within three BAU’s (see map).

          Area 1 (pale green) includes all of Donegal, North Leitrim and North Sligo.

          Area 2 (purple) is all of Mayo, west Galway, all of Roscommon and West Sligo.

          Area 3 (yellow) is south Leitrim, Cavan, Monaghan, Louth, Meath, Westmeath,

                            Offaly and north Laois.

Within the Business Area Units there are ‘Forest Management Units’ that are managed from day to day at a local level with Sligo having 12 and Leitrim having 12 such ‘Forests’.


A year after his death, an Atlas drawn by Mercator gave a slightly more accurate portrayal of Ireland than in the 1570 map.


Baptista Boazio drew a map of all of Ireland which is reproduced in the end papers of the ‘Atlas of Ireland’ (Irish National Committee for Geography 1979).  The depiction of the coast of Sligo and place names have hardly changed from Mercator’s 1595 map.


Richard Bartlett produced a detailed map of Tyrconnell and for the first time depicted the coast of Sligo with some accuracy and named quite a few places.  He drew the hills of ‘Benbolbin’ and noted that there was a falcon to be seen here!  The forested nature of the land to the north of Glencar Lough was also drawn on the map.  Another difference from the maps shown above is that north is at the top of the page.  After 30 years of cartographers re-drawing the same basic map, Bartlett seems to have added significantly to the knowledge of Ireland.


A copper plate engraved in 1572 was found in Armagh in the nineteenth century from which the map shown below was printed.  It is not known who the cartographer was but it is very likely the source of the map that was used by Mercator (as shown above).  Details from these two maps for the Sligo region are shown side by side below this and the similarity between them is obvious.

Sligo region from 1572 Armagh map

Sligo region from 1570 Mercator map


John Norden produced a map of Ireland ‘The Plott of Irelande with the Confines’ which again is derived from Boazio’s map that was itself closely following Mercator’s 1595 map.  It is a shame that he didn’t take note of the Bartlett map.


John Speed's maps were based on Mercator's Atlas of 1595 and Baptista Boazio's map of Ireland and other regional sources.


Before printed books became widespread it was the habit to make hand drawn copies of pre-existing maps.  The map shown below was clearly taken from the ones above but included more place names and showed a more accurate coastline, especially for Kerry and Cork.  It is therefore likely to be a little more recent than 1572.

Topics within this page :








Biological Sea Areas

The sea ecosystem shows a considerable degree of uniformity over wide areas and so marine biologists tend to use a larger scale for their recording purposes.

Sea Areas or Marine Census Areas

Heppell (1964) divided the sea and sea shore around Great Britain and Ireland into 48 'Sea Areas' to assist biologists in the handling of data and the plotting of distribution maps (see basic map).  The shores and inshore waters of Sligo and Leitrim fall within Sea Area 34 Donegal Bay which has the boundaries defined as "55o0'N; Coast of Ireland including Broadhaven to Erris Head; 10o0'W".  Thus everything from Aran Island in northern County Donegal right around to Erris Head in County Mayo is included in this Sea Area.  Conchologists (people who study of snails and bivalves), crab specialists and others have used these divisions and appointed official recorders for each area.  For Phylum Mollusca Sea Area 34 is administered by Mrs E. Platts, Tiverton, Quarry Road, Belfast, BT4 2NP; it previously having been administered by Dr L.S. Garrad.  The atlas published by Seaward (1982) was based upon this sea area division and Ingle’s book on crabs (1982) used this system. This system is actually more suitable for use in the Sligo-Leitrim area

The ‘Real’ Map of Ireland

In the 2000’s the importance of the sea around our coast as a natural resource led to the following map being produced and promoted by the Department of the Marine and the Government of Ireland :

Ocean Currents

The surface currents of the seas off the west coast of Ireland have a major impact on the climate of this country.  Huge quantities of warm sea water pass our coast on the way from tropical to arctic areas and ameliorate our climate.  The following map shows modern mapping of these currents.  The thick red line is the North Atlantic Drift which is an off-shoot of the Gulf Stream.

Water Framework Directive, River Basin Districts

Western River Basin District (WRBD)


Lord Burghley as Chief Minister in Elizabethan times collected maps of Ireland which were very crude.  He employed surveyors to make corrections with an emphasis on strategic features such as river crossings, mountain passes etc. (Moody & Martin 1967 page 24).  For example, Sir Richard Bingham was appointed as President of Connaught and had a map prepared, probably by John Browne, to help in the campaign of consolidating English dominance in the region of Sligo.  This map is still extant in The Public Records Office of London and was recently reproduced in Swift (1999).  Of some interest is the marking of three Spanish ship wrecks off Streedagh which sank just a year earlier in 1588 after the failure of the Spanish Armada.

In the first half of 1836 John O'Donovan was sent to Cos. Cavan and Leitrim to gather information about place names, monuments and the people of these counties and on the 2nd of July 1836 he was sent to County Sligo to continue the same process.

Once all of the data had been collected it was then time to compile and publish the findings.  Captain Thomas Larcom of the Ordnance Survey began this task during the early years of Queen Victoria's rule (1837 onwards) when official maps, memoirs and statistical reports were prepared (Moody & Martin 1967 page 26).

The first detailed maps on a scale of 1:10,560 (6 inches to the mile) were published in 1837 and from then up to 1842, 1,906 maps at this scale were published that covered the entire country.  These are sometimes referred to as the 1st edition.  Each sheet was three feet by two feet (909 mm x 606 mm) and represented 24 square miles (about 61 km2).  Using these maps the tax liability of land owners was duly carried out by Richard Griffith which is known to historians as the 'Griffith evaluations'.

Another important aspect of mapping is to determine the heights above sea level of the various features.  In order to do this the Ordnance Survey carried out a massive leveling exercise over the whole country between 1839 and 1843 and established many bench marks based upon a measurement of sea level at Poolbeg in Dublin.  The main road of the time from Dublin to Sligo via Carrick-on-Shannon, Boyle and Ballysadare was used to link east and north-west coasts with a continuation north to Cliffony and thence down to the sea at Mullaghmore where a tide station was established for local sea level determination.  Going westwards, the leveling was taken along the coast road from Ballysadare to Ballina.

A revision of the 1839-1843 series of maps was completed in 1888 (2nd edition) and between 1900 and 1915 the 3rd edition of the 6 inches to 1 mile maps were published.  The works of these cartographers are still in use today in the form of the 25 inch and 6 inch sheets of the Ordnance Survey.  They are still being updated and are often used in planning applications for new buildings.

[The preceding information was gleaned from National Library of Ireland (1980) &

Irish National Committee for Geography (1979)].

A new series of maps at the very detailed scale of 1:2,500 (approximately 25 inches to the mile) was begun in 1888 and the set of maps for County Sligo was published between 1909 and 1912 that included a town plan of Sligo published in 1910.  Some of these sheets were revised between 1940 and 1942.

In parallel with these large scale maps another series of maps more appropriate for travelers were drawn up on a scale of 1 inch to the mile (1:63,360) during the period 1855-1900.  These large scale maps required 205 sheets to cover the entire country with counties Sligo and Leitrim falling on 17 sheets in the range between map numbers 31 and 79 (see Index map shown below).

Example of the mapping style of ‘John The Map’ with the town map for Drumshanbo, County Leitrim


In 1824 the Ordnance Survey who had already surveyed Great Britain were charged with the duty of preparing large scale maps for the whole of Ireland so that land ownership could be valued for taxation liability.  A team of over 2000 men under the direction of Major Thomas Frederick Colby was assembled and between 1825 and 1833 they accurately determined the shape of the entire island using a series of triangulation stations in what is known as the Principal Triangulation of Ireland.  These stations were established at high places that had a direct sight line to other such stations.  In the Sligo/Leitrim region Knockalongy situated in the Ox Mountains above Skreen was selected.  In 1828 measurements were made from Knockalongy northwards to Slieve League in Donegal, eastwards to Cuilcagh in Cavan, westwards to Tawnaghmore on the north Mayo coast, south-westwards to Nephin in Mayo, and the huge distance of 170 km south to Keeper Hill near Limerick.  Cuilcagh that lies in Cavan just over the Leitrim border, was also selected in 1828 and used in a similar way.

Principal Triangulation of Ireland

Detail of Sligo / Leitrim area

from Principal Triangulation of Ireland

The triangulation exercise was repeated between 1958 and 1969 when Truskmore was added to the primary triangulation stations in this region and more accurate measurements were obtained.  As with the triangulation, the leveling was repeated between 1958 and 1969 using different routes and Fundamental Bench Marks were established at Ballysadare and Inishcrone.

Irish Grid (IG)

In 1952 a grid system had been devised and was in use as the ‘Military Grid’ but it was not overprinted on maps for use by the general public.  This was modified to become the Irish Grid which was eventually printed on the 1:126,720 (half inch to the mile) series when they started to be published in the 1970’s.

1:126,720 (half inch to the mile)

The maps commonly in use in the 1970's and through most of the 1980's were the so-called "half-inch" series which were at a scale of half and inch to the mile of approximately 1 cm to 1.25 km.  These were published by the Ordnance Survey, Dublin and Sheet No.7 'Sligo and Leitrim' covers most of this area but Sheet No.3 'S.Donegal' and Sheet No.6 'Mayo' also took in some of the area.  A map to the same scale produced by the Ordnance Survey of Northern Ireland "Sheet No.3 The South-West" was actually more suitable for use in Sligo and Leitrim than the ones published by the Irish O.S. in Dublin.

1:50,000 (2 cm to one kilometer)

In 1992 the Ordnance Survey at the Phoenix Park in Dublin published the first of their new series of maps which were produced using digital technology.  These were the Rambler Series and Sheet 16 covering the north county Sligo area was a huge improvement on the previous 'half-inch' maps although it was not without its faults (Cotton & Thorn 1993).  The Rambler Series of maps were to some extent experimental and after a few were produced the series was replaced by the Discovery Series on the same scale but with a better use of colour.  A major criticism of this series is the poor quality of paper they are produced on which results in a map lasting for less than a year if it is in regular use.  Maps in the Discovery Series which include parts of Sligo and Leitrim are :

16Sligo, Leitrim, Fermanagh & Donegal

17    Lower Lough Erne

24Mayo & Sligo

25Sligo, Leitrim & Roscommon

26Cavan, Fermanagh, Leitrim, Roscommon & Sligo

27(tiniest corner of Leitrim)

27ACavan, Fermanagh, Leitrim & Monaghan

32Mayo, Roscommon & Sligo

33Leitrim, Longford, Roscommon & Sligo

34Cavan, Leitrim, Longford, Meath & Westmeath

Maps produced by the Ordnance Survey of Northern Ireland are (the numbering system is common to both Ordnance Survey organisations) :

17Lower Lough Erne

26Lough Allen

27Upper Lough Erne

Index to the one inch series of maps (1:63,360)

[Note : the historical one inch series and town plans were re-published by Phoenix maps in 1989]

Teagsc (Agriculture and Food Development Authority)

This state organisation researches and advises the agriculture and food production sectors of the Irish economy.  An important part of their brief is to build principles of sustainability into everything that they do; something that should be beneficial to wildlife.  Education is also a major part of their role.  The map below shows counties Sligo and Leitrim as falling into the border region along with counties Donegal, Cavan, Monaghan and Louth.  In this respect they operate over a similar geographical area to the National Parks and Wildlife Service.  Local offices are at Riverside in Sligo town and at Mohill in County Leitrim.

National Parks & Wildlife Service Ranger Areas

Information not currently available as a map.

Sligo and Leitrim are overseen by a District Conservation Officer who also administers County Donegal.  He managers the Conservation Rangers of which there is one in North Leitrim but none in any part of County Sligo.

Inland Fisheries Ireland districts are the same as the River Basin Districts used by the Environment Protection Agency and others.  The outlines of County Sligo and County Leitrim are shown by a thin white line.  The IFI also patrol and monitor a marine area extending approximately 20 km (12 miles) out to sea.