Lexington is a city in Lafayette County, Missouri, United States. The population was 4,726 at the 2010 census. It is the county seat of Lafayette County. Located in western Missouri, Lexington lies approximately 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 of the former Wentworth Military Academy and College, the second-oldest military school west of the Mississippi River, opened in 1880.