The Squannacook River Rail Trail is a partially completed 3.7 mile recreational trail in Townsend and Groton, Massachusetts. The trail parallels the Squannacook River and runs next to the Squannacook River State Wildlife Management Area and Townsend State Forest. It also passes through historic Townsend Harbor, passing three buildings owned by the Townsend Historical Society, the Cooperage, the Grist Mill, and The Reed Homestead. The nonprofit Squannacook Greenways has spearheaded the effort to build and maintain the rail trail since 2011.

The Squannacook River Rail Trail is the conversion of an abandoned section of the spur off the Fitchburg railroad line to Greenville, New Hampshire, which was originally called the Peterborough and Shirley. The spur reached Townsend center in 1846, and the state border by 1850, ending in the center of Greenville, just after crossing a dramatic steel trestle bridge across the Souhegan River. It served both as a means of transportation for the people of West Groton, Townsend, Mason, and Greenville, and as a freight carrier for the many water-powered industries along the Squannacook and Souhegan rivers.

Photo courtesy of Squannacook Greenways