Longford, county (1991 pop. 30,296), 403 sq mi (1,044 sq km), N central Republic of Ireland. The county seat is Longford. A part of the central plain of Ireland, it has level land with numerous small lakes, bogs, and marshes. The River Shannon and Lough Ree form its western border. Raising beef cattle is the principal occupation; oats and potatoes are the chief crops.