A city and the county-seat of Posey county, Indiana, U.S.A., on the Ohio river, in the extreme south-west corner of the state. Pop. (1890), 4705; (1900), 5132, of whom 892 were negroes and 262 were foreign-born. It is served by the Evansville & Terre Haute, the Louisville & Nashville, and the Evansville & Mount Vernon (electric) railways. The city is a trading centre for the surrounding farming region. It has a valuable river trade, and various manufactures. The first settlement here was made in 1803, and in 1819 a town was laid out and named Mount Vernon. It became the county-seat in 1825, and was incorporated as a town in 1846 and chartered as a city in 1865.