Union county is in the Western Coal Field region of Kentucky. The elevation in the county ranges from 320 to 673 feet above sea level.
In 2010 the county population was 15,007 in a land area of 342.85 square miles, an average of 43.8 people per square mile.
The equine population was 1,100 in the 2012 Kentucky Equine Survey.
Union county was probably named to symbolize the united will of the residents.