LEITRIM, a county of Ireland in the province of Connaught, bounded north-west by Donegal bay, north-east by Fermanagh, east by Cavan, south-east by Longford, south-west by Roscommon and west by Sligo. Area 392,381 ac. or about 613 sq. miles. Pop. (1926) 55,888.
The county has a floor of Carboniferous Limestone, which forms scarped hills near Donegal bay. The northern part of the county is a tableland, of which the highest summits belong to the Trusk more hills, reaching 1,712 ft.; with Benbo, 1,365 ft. and Lackagh 1,446 feet. The underlying sandstone appears at Lough Melvin, and again on the margin of a Silurian area in the extreme south. The Upper Carboniferous series, dipping southward, form moun tainous country round Lough Allen, where the name of Slieve Anierin records the abundance of clay-ironstone beneath the coal seams. The sandstones and shales of this series scarp boldly towards the valley of the Bonnet, across which rises the ridge of ancient gneiss which forms, in Benbo, the north-east end of the Ox mountains. The ironstone was smelted in the upland at Cree velea down to 1859, and the coal is worked in a few thin seams.
The principal river is the Shannon, which, issuing from Lough Allen, forms the south-western boundary of the county with Ros common. The Bonnet rises in the north-west and flows to Lough Gill, and the streams of Drones and Duff separate Leitrim from Donegal and Sligo. Besides Lough Allen, which has an area of 8,90o ac., the principal lakes are Lough Macnean, Lough Scur, Lough Garadice and Lough Melvin. Lough Melvin and the coast rivers afford rod fishing, the lough being noted for its trout.
Co. Leitrim, under the name of Hy Bruin-Brenny, formed the western part of Brenny or Breffny. It was for a long time held by the O'Rourkes, a family which long maintained its independence. Leitrim was not created a county until 1583. Large confiscations were made in the reigns of Elizabeth and James I., in the Crom wellian period, and after the Revolution of 1688.
There are "druidical" remains near Fenagh and at Letterfyan, and monastic ruins at Creevelea near the Bonnet, and in the parish of Fenagh. There was a Franciscan friary at Jamestown. The abbeys of Mohill, Annaduff and Drumlease have been converted into parish churches. Among the more notable old castles are Manor Hamilton now in ruins, and Castle John on an island in Lough Scur. A village named Leitrim about 4 m. N. of Carrick on-Shannon is said to have been the seat of an early bishopric.
The climate is moist and unsuitable for grain crops. On the higher districts the soil is stiff and cold, and retentive of moisture, but some valleys are fertile. Lime, marl and similar manures are abundant. Potatoes are grown, but oats, the principal grain crop, are scanty. The live stock consists chiefly of cattle, pigs and poultry. Coarse linens for domestic purposes are manufactured and coarse pottery is also made. The Sligo, Leitrim and Northern Counties railway, connecting Sligo with Enniskillen, crosses the north of the county, by way of Manor Hamilton ; the Mullingar and Sligo line of the Great Southern has a station at Carrick-on Shannon ; while connecting with this line at Dromod is the line to Ballinamore and Arigna, and to Belturbet in Co. Cavan. The administrative counties of Leitrim and Sligo together return seven members to Dail Eireann.
The territory now included in Co. Leix covered the districts of Leix, Slewmargy, Irry and part of Glenmaliry, until in 1556 it was made shire ground. Three miles south of Stradbally is Dun of Clopook, an ancient dun or fort occupying the whole extent of the hill. Aghaboe, where there are the ruins of the abbey, was formerly the seat of the bishopric of Ossory. There are no remains of the abbey of Timahoe founded by St. Mochua in the 6th century, but in the neighbourhood there is a round tower, 96 ft. high. Abbeyleix, a small market town south of Mary borough, had a famous 12th century Cistercian foundation. The church of Killeshin, in the south-east of the county, exhibits Norman carving. Among the principal old castles are the ruined fortress of the O'Mores occupying the precipitous rock of Duna mase, 3 m. E. of Maryborough, Borris-in-Ossory on the Nore, and Lea Castle on the Barrow, near Portarlington, erected by the Fitzgeralds about 1260, burnt by Edward Bruce in 1315, again rebuilt, and in 1650 laid in ruins by the soldiers of Cromwell.
Originally a great extent of the surface was occupied with bog, but much has been recovered by draining. It is generally fertile except in the hilly districts towards the north, and there is some remarkably rich land in the south-east. Dairy farming is ex tensively practised. Agriculture forms the chief occupation, but the manufacture of woollen and cotton goods is carried on to a small extent. The main line of the Great Southern railway traverses the county from north-east to south-west by way of Portarlington and Maryborough ; from the latter town branches run north to Mountmellick and south to Waterford, and from Ballybrophy a line runs west to Birr (Parsonstown) and to Limerick. The administrative counties of Leix and Offaly to gether return five members to Dail Eireann. The county town is Maryborough (Port Laoighise) with a population of 3,272.