Mount Vernon is a city in and the county seat of Posey County, Indiana, United States. Located in the state's far southwestern corner, within 15 miles of either the southernmost or westernmost points it is the westernmost city in the state, but not the southernmost, that being Rockport, about 40 miles to the southeast. The population was 6,687 at the 2010 census. It is located in Black Township and is part of the Evansville, Indiana, metropolitan area, which had a 2010 population of 358,676.