TYRONE, a county of Ireland in the province of Ulster, bounded north and west by Donegal, north-east by Londonderry, east by Lough Neagh and Armagh and south by Monaghan and Fermanagh. The area is 806,658 acres or about 1,260 sq.m. Pop. (1926) 132,777. Running along the north-eastern boundary with Londonderry are the schist ridges of the Sperrin Mountains (Sawel, 2,240 ft., and Meenard, 2,061 ft.). Most of the south of the county is occupied by sandstone formations. Mullaghearn, north-east of Omagh, reaches 1,778 ft. South of Clogher a range of hills, reaching 1,255 ft. in Slieve Beagh (Upper Carboniferous sandstones and shales), forms the boundary between Tyrone and Monaghan.
From Coalisland to Dungannon true Coal Measures appear. This coalfield includes one seam 9 ft. thick at Coalisland; less important coals occur in the Millstone Grit series at Dungan non. The field doubtless continues eastward under the Triassic sandstone that stretches towards Lough Neagh. The pale clays, probably Pliocene, of the southern shore of the lake cover the flat land east of Coalisland, and are several hundred feet thick. North of Stewartstown, near Tullaghoge, a very small patch of Magnesian limestone contains Permian marine fossils; and, far ther north, the county includes part of the basaltic plateaux, pro tecting Chalk, which extend into co. Londonderry.
The Foyle forms a small portion of the western boundary of the county, and receives the Mourne, which flows northward by New ton Stewart. The principal tributaries of the Mourne are the Strule (constituting its upper waters), the Derg from Lough Derg, and the Owenkillew, flowing westward from Fir Mountain. The Blackwater rises near Fivemiletown and forms part of the south-eastern boundary of the county with Monaghan and Armagh. Lough Neagh bounds the county on the east. Lough Fea is situ ated in the north-west, and there are several small lakes near Newtown Stewart.
Tyrone became a principality of one of the sons of Niall of the Nine Hostages in the 5th century, and from his name—Eogan —was called Tir Eogan, gradually altered to Tyrone. From Eogan were descended the O'Neals or O'Neills and their numer ous septs. The family had their chief seat at Dungannon until the reign of Elizabeth, when it was burned by Hugh O'Neill to prevent it falling into the hands of Lord Mountjoy. The earldom of Tyrone had been conferred by Henry VIII. on Conn O'Neill, but on his death, when the earldom should have descended to his heir Matthew, baron of Dungannon, another son, Shane, was pro claimed chief with the consent of the people. Shane defied English
authority, but his forces were defeated near the river Foyle in 1567, and shortly afterwards he was himself killed. Tyrone was one of the counties formed at Sir John Perrot's shiring of the unreformed parts of Ulster; but his work was interrupted by the rising of Hugh O'Neill in 1596. During the insurrection of 1641 Charlemont Fort and Dungannon were captured by Sir Phelim O'Neill, and in 1645 the parliamentary forces under General Munro were defeated by Owen Roe O'Neill at Benburb. At the Revolution the county was for a long time in the possession of the forces of James II.
Raths are numerous in the county. There is a large cromlech near Newtown Stewart, another at Tarnlaght near Coagh and another a mile above Castlederg. At Kilmeillie near Dungannon are two stone circles. There are some ruins of the ancient castle of the O'Neills, near Benburb ; mention may also be made of the ruins of the castles of Newtown Stewart, Dungannon, Strabane and Ballygawley. The hill pastures support a large number of young cattle. Oats, potatoes and turnips are the principal crops. The cultivation of flax, formerly an important industry, has greatly deteriorated. Poultry-keeping is a growing industry. There are manufactures of linens and coarse woollens (including blan kets) ; brown earthenware, chemicals, whiskey, soap and candles are also made. There are a few breweries and distilleries.
Branches of the Great Northern railway from Portadown (Co. Armagh) and Dungannon in the south-east, and from Enniskillen (Co. Fermanagh) and Fintona, unite at Omagh, whence a line proceeds north by Newtown Stewart and Strabane to London derry. From Dungannon a branch runs north to Cookstown, where it joins a branch of the Northern Counties (Midland) railway. From Victoria Bridge on the Londonderry line the Castlederg light railway serves that town. The south of the county is served by the Clogher Valley light railway. Water com munication includes Lough Neagh, and the Blackwater entering it, and navigable to Moy, whence the Ulster canal skirts the boundary of the county with Co. Armagh to Caledon.
The administrative counties of Tyrone and Fermanagh together return 8 members to the Parliament of Northern Ireland and 2 members to the Parliament of Great Britain.