The county is bordered by Hopkins, Muhlenberg, Todd, Trigg, and Caldwell counties and by Tennessee. Covering 722 square miles, Christian County is the second-largest in the state (45 miles long and 25 miles wide). The county seat is Hopkinsville.

Christian County was formed from a portion of Logan County by the Kentucky General Assembly in 1796 and organized on March 1, 1797. The new county was named in memory of Col. William Christian, a native of Augusta County, Va., and a veteran of the American Revolution. He settled on Beargrass Creek near Louisville in 1785 and was killed by Indians in southern Indiana the following year.

Originally, the county included all land north of the Tennessee line, west of Logan County and the Green River, south of the Ohio River and east of the Tennessee River. All the counties now in this area were formed out of Christian County between 1798 and 1860.

James Davis and John Montgomery made the first permanent settlement in the county around 1784. They brought their families by flatboat down the Ohio River and then up the Cumberland River to settle on Montgomery Creek, southeast of present-day Pembroke. There the settlers built a log blockhouse on land where they hunted and farmed.

In the next two decades, settlement concentrated in northern Christian County, which had abundant fresh water, wild game and timber for building and for fuel. Poor road conditions, the struggle for existence, and the land's topography isolated the valley settlements.

The flat, fertile land in southern Christian County was settled in the first quarter of the 19th century. Rich clay soil with a foundation of limestone was well-suited for crops, especially dark tobacco. Most of the land was barren of trees and covered in prairie grass, with a few springs along Little River and West Fork of the Red River. Large farms supported by slave labor were patterned after those in the Tidewater and the Deep South. Both sections of the county were fully settled by 1830, when the population reached 12,684.