Boyle County was formed from a portion of Casey County which is south of old KY Route 300, the same land that was annexed to Mercer County. Officially formed on February 15, 1842, it is named after John Boyle who is a former congressman, chief justice of the Kentucky Court of Appeals, and a former U.S. District Judge. Sitting on 183 square miles, it is home to 30,100 residents.