Union County is a county located in the U.S. state of Florida. Its county seat is Lake Butler. Union County was created in 1921 and was named to honor the concept of unity. Union County is the location of Union Correctional Institution. Union CI is a maximum-security prison and is home to part of Florida's Death Row. Union County has a total area of approximately 250 square miles of which 96% is land and 4% water. As of the 2000 census, there were 13,442 people, 3,367 households, and 2,606 families residing in Union County, FL.