It was formed in 1792 from Lincoln county. The county seat is Russellville. Logan county was a source of Christian (1797), Warren (1797), Muhlenberg (1799), Butler (1810), Simpson (1819), and Todd (1820) counties.
In 2010 the county population was 26,835 in a land area of 552.13 square miles, an average of 48.6 people per square mile.
The equine population was 1,700 in the 2012 Kentucky Equine Survey.
Logan county was named for General Benjamin Logan, who served in the American Revolution.