Ayer's history dates back to 1667, when the first mill in the agricultural community was built. The settlement sits on what the Nipmuc Indians called Nainacocius. Originally part of Groton,the community was initially called Groton Junction or South Groton. The town of Ayer was incorporated in 1871, and was named in honor of Dr. James Cook Ayer, a prominent resident of Lowell who provided the funding for the construction of the Town Hall.
Regional Rail Hub : The town's growth was influenced by a period of rapid development of railroad transportation. Though only 9.5 square miles (25 km2) in area, the town became a major junction for both east-west and north-south rail lines, and developed into an important commercial center oriented towards the rail industry.
Military Roles : 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 1996, but was reopened the next day as a reserve training area. It has since been reopened, although on a much smaller scale then the days when it was active.
Ski Jump : In 1935, the largest Nordic ski jump in North America was constructed at Pingry Hill near the Willows. A 700-foot-high wooden trestle build, the ski jump operated for a single winter season amid the hardships of Great Depression-era Ayer. Part of the structure was blown down by the wind in the summer of 1936 and it was never rebuilt. Some of the lumber was salvaged by local residents over the next few years. As of 2013, no trace of the massive structure remains.