Ayer's history dates back to 1667 when the first mill, used to grind corn in the agricultural community, was built. Originally part of the town of Groton, Ayer was incorporated in 1871 and named in honor of Dr. James Cook Ayer, a prominent resident of Lowell who provided the funding for the construction of Town Hall (1873-76). The Town's growth was influenced by a period of rapid development of railroad transportation during the mid 19th century. Though only 9.5 square miles in area the Town became a major junction for both east-west and north-south rail lines, and developed into an important commercial center.
During the Civil War an army training camp, Camp Stevens, was located near the Nashua River. Camp Devens, which eventually became Fort Devens, was established in 1917, during World War I. The presence of thousands of military and civilian personnel on the base shifted Ayer's commercial development towards meeting their needs until Fort Devens was closed in 1994.
The Town today is a reflection of its history. Within its relatively small area the Town boasts numerous industries, a thriving, historical downtown, unique to the region and modern commuter rail service to Boston.