Lewis County is a county located in the U.S. state of Kentucky. As of the 2020 census, the population was 13,080. Its county seat is Vanceburg. The area presently bounded by Kentucky state lines was a part of the U.S. State of Virginia, known as Kentucky County when the British colonies separated themselves in the American Revolutionary War. In 1780, t…Lewis County is a county located in the U.S. state of Kentucky. As of the 2020 census, the population was 13,080. Its county seat is Vanceburg. The area presently bounded by Kentucky state lines was a part of the U.S. State of Virginia, known as Kentucky County when the British colonies separated themselves in the American Revolutionary War. In 1780, the Virginia legislature divided the previous Kentucky County into three smaller units: Fayette, Jefferson, and Lincoln. In 1791, this area was separated into the State of Kentucky; it became effective on June 1, 1792. From that time, the original three counties were divided several times. A portion of Fayette County was split off as Bourbon County in 1785; a portion of Bourbon was split off as Mason County in 1788; in 1806 the present Lewis County was split off from Mason. The new county was named for Meriwether Lewis.