Lexington is a town in Middlesex County, Massachusetts, United States. The population was 31,394 at the 2010 census, in nearly 11,100 households. Settled in 1641, it is celebrated as the site of the first shots of the American Revolutionary War, in the Battle of Lexington on April 19, 1775. It is part of the Greater Boston Area and is the sixth wealthiest small city in the United States.