In the early colonial days, Vine Brook, which runs through Lexington, Burlington, and Bedford, and then empties into the Shawsheen River, was a focal point of the farming and industry of the town. It provided for many types of mills, and in the 20th Century, for farm irrigation.
For decades, Lexington grew modestly while remaining largely a farming community, providing Boston with much of its produce. It always had a bustling downtown area, which remains to this day. Lexington began to prosper, helped by its proximity to Boston, and having a rail line (originally the Lexington and West Cambridge Railroad, later the Boston and Maine Railroad) service its citizens and businesses, beginning in 1846 (As of 2015, the Minuteman Bikeway occupies the site of the former rail line). For many years, East Lexington was considered a separate village from the rest of the town, though it still had the same officers and Town Hall. Most of the farms of Lexington became housing developments by the end of the 1960s.
Lexington is located at 42°26′39″N 71°13′36″W (42.444345, -71.226928). According to the United States Census Bureau, the town has a total area of 16.5 square miles (42.8 km²), of which 16.4 square miles (42.5 km²) is land and 0.1 square miles (0.4 km²), or 0.85%, is water. Lexington borders the following towns: Burlington, Woburn, Winchester, Arlington, Belmont, Waltham, Lincoln, and Bedford. It has more area than all other municipalities that it borders.