Lexington is a city in Lafayette County, Missouri, United States. The population was 4,453 at the 2000 census. It is the county seat of Lafayette County. Located in western Missouri, Lexington lies about 40 miles east of Kansas City and is part of the Greater Kansas City Metropolitan Area. It is the home of the Battle of Lexington State Historic Site, and Wentworth Military Academy and College, the oldest military school west of the Mississippi River.