Offaly (ŏfˈəlē) [key], county (1991 pop. 58,494), 771 sq mi (1,997 sq km), central Republic of Ireland. The county seat is Tullamore. A part of the central plain of Ireland, the county is mostly flat with some sections covered by the Bog of Allen. The Slieve Bloom Mts. are on the southeastern border. The Shannon, the chief river, forms much of the western border. Other rivers are the Brosna and Blackwater. Agriculture is the chief occupation; cattle, pigs, and poultry are bred in considerable quantity. Grains and potatoes are grown. Among the light industries is distilling. With adjacent areas, the region formed the kingdom of Offaly in ancient Ireland. It was known as King's County until the establishment of the Irish Free State. At Clonmacnoise are the ruins of one of the principal religious centers of early Ireland.