Louisville is the most populous city in the Commonwealth of Kentucky, sixth-most populous city in the Southeast, and the 28th-most-populou…Louisville is the most populous city in the Commonwealth of Kentucky, sixth-most populous city in the Southeast, and the 28th-most-populous city in the United States. By land area, it is the country's 24th-largest city; however, by population density, it is the 265th most dense city. Louisville is the historical county seat and, since 2003, the nominal seat of Jefferson County, on the Indiana border.