Acton is a town in Middlesex County, Massachusetts, United States, approximately 21 miles west-northwest of Boston along Massachusetts Route 2 west of Concord and about ten miles southwest of Lowell. The population was 24,021 in April 2020, according to the United States Census Bureau. It is bordered by Westford and Littleton to the north, Concord and Carlisle to the east, Stow, Maynard, and Sudbury to the south and Boxborough to the west. Acton became an incorporated town in 1735.