Donegal (dŏnˌĭgôlˈ, dŭnˌ–) [key], county (1991 pop. 128,117), 1,865 sq mi (4,830 sq km), N Republic of Ireland, on the Atlantic Ocean. The county seat is Lifford. The extremely irregular coastline extends from Lough Foyle on the north to Donegal Bay on the west and is deeply indented by Lough Swilly. Tory Island is the largest of the coastal islands. The west is rugged and hilly. There are two mountain ranges: the Derryveagh Mts. in the northwest and the Blue Stack Mts. in the west central region. Mt. Errigal (2,466 ft/752 m) is the tallest peak. The chief rivers are the Foyle, the Erne, and the Finn; lakes are plentiful. Donegal has no rail service. Although agriculture is the leading industry, only one third of the land is suitable for cultivation. The valleys of the Finn and the Foyle are the most intensively cultivated areas. Oats and potatoes are the chief crops. Fishing and tourism are also important industries. In the south is the center of the Donegal cloth industry that produces tweeds and handmade woolens. There are several small skirt factories. Newer industries include carpet, fishing net, and synthetic fiber manufacturing. Gaelic is still spoken in the highland region. In ancient times the kingdom of Tyrconnell, Donegal was not organized as a county until the reign of Elizabeth I of England.