Kentucky County (then alternately spelled Kentucke County) was formed by the Commonwealth of Virginia from the western portion (beyond the Cumberland Mountains) of Fincastle County effective December 31, 1776. The name of the county was taken from a Native American place name that came to be associated with a river in east central Kentucky, and gave the Kentucky River its name. During the three and one-half years of Kentucky County's existence, its seat of government was Harrodstown (then also known as Oldtown, later renamed Harrodsburg).

Kentucky County was abolished on June 30, 1780, when it was divided into Fayette, Jefferson, and Lincoln counties. Afterward, these counties and those set off from them later in that decade were designated collectively as the District of Kentucky by the Virginia House of Delegates. The counties of the district frequently petitioned both the Virginia legislature and the Continental Congress seeking statehood. Finally successful, the Commonwealth of Kentucky was admitted to the United States as the 15th state in 1792.