The Bay Circuit Trail and Greenway is a partially completed 230-mile multi-use trail that runs through thirty-seven cities and towns in Massachusetts, beginning at Plum Island in Newbury and ending at Kingston Bay in Duxbury. Within Freedom’s Way National Heritage Area, the trail serves the communities of Acton, Bedford, Concord, Lincoln, Sudbury, and Westford.

The idea for the Bay Circuit Trail and Greenway first arose in 1929. It would be an “outer Emerald Necklace,” proponents said—a greenbelt that would mirror the famous string of Frederick Law Olmsted-designed parks threading through urban Boston—and would provide open space for the metropolitan area’s quickly expanding population. Over the next several decades, various public and private parks and reservations were established in the area between what is now Route 128 and Interstate 495, but they failed to keep pace with commercial and residential development. In the 1980s, interest in the project was renewed, and in 1990 the Bay Circuit Alliance (BCA) formed to make the trail and greenway a reality. The BCA has focused on linking segments of the Bay Circuit Trail, which provides a place for recreation while ensuring the protection of open space in the region by adding more “pearls” to the “emerald necklace.”

The trail provides close-to-home recreation including walking, biking, snowshoeing, horseback riding and cross-country skiing. Many sections of the trail are accessible by the MBTA commuter rail and other public transit systems.

Since 2012, the Appalachian Mountain Club has led the Alliance in the completion, enhancement, and long-term protection of the recreational trail and greenway. The AMC works with the Alliance to fulfill the vision of the Bay Circuit by closing the final gaps of the trail, recruiting and organizing volunteers, improving the trail experience through improved maintenance and signage, securing permanent protection for the trail corridor and the greenway, and encouraging the public to get out and explore all the trail has to offer.