Chelmsford is a town in Middlesex County, Massachusetts in the Greater Lowell area. As of the 2010 United States Census, the town's population was 33,802. Only 48.4 re male and the median age of residents in Chelmford is 39.2 years old. It is located northwest of Boston and, bordering on the city of Lowell, is part of the Greater Lowell metropolitan area. Besides Lowell on its northeast, Chelmsford is surrounded by four towns: Tyngsborough to the north, Billerica to the southeast, Carlisle to the south, and Westford to the west. Chelmsford is bordered by two sizable rivers: the Merrimack River to the north, and the Concord River to the east.