Allen County is a county located in the U.S. state of Kentucky. As of the 2020 census, the population was 20,588. Its county seat is Scottsville. The county is named for Colonel John Allen, a state senator and soldier who was killed leading the 1st Regiment of Kentucky Rifleman at the Battle of Frenchtown, Michigan during the War of 1812. Allen County practices the prohibition of alcohol and is a completely dry county. It was formed in 1815 from parts of Barren and Warren counties. Allen County is included in the Bowling Green, KY Metropolitan Statistical Area.