|Bay Circuit Trail|
|Length||200 mi (322 km)|
|Location||Plymouth County, Middlesex County, eastern Worcester County, Bristol County and Essex County, Massachusetts|
|Highest point||Nobscot Hill, Framingham, Massachusetts, 602 ft (183 m)|
|Lowest point||Sea level, north and south terminus|
|Trail difficulty||easy with some moderately difficult sections|
|Season||year round (may be ice or snow in winter)|
|Hazards||deer ticks, poison ivy, road crossings|
|Maintained by||Bay Circuit Alliance|
The Bay Circuit Trail and Greenway or Bay Circuit is a Massachusetts rail trail and greenway connecting the outlying suburbs of Boston from Plum Island in Newburyport to Kingston Bay in Duxbury, a distance of 200 miles (320 km).
Landmarks include Henry David Thoreau's Walden Pond, Great Meadows National Wildlife Refuge, the Charles River, Massachusetts Audubon's Moose Hill Wildlife Sanctuary, Minute Man National Historical Park, Lowell National Historic Park, the Merrimack River, and Plum Island.
The Bay Circuit Trail connects to other long distance recreation trails, such as the Warner Trail. The Minuteman Bikeway will provide a connection to downtown Boston when the Somerville Community Path is completed. The East Coast Greenway will also connect downtown if it is completed as envisioned.
The Bay Circuit is open to hiking, trail running and picnicking, and in the winter, snowshoeing. Certain parts of the trail are suitable for bicycling, horseback riding and cross country skiing. Swimming, mountain biking, hunting, fishing, and car top boating are also permitted in some properties the trail passes through.
The Bay Circuit Trail is overseen by the Bay Circuit Alliance, a coalition of state, town, and federal agencies, non-profit organizations, and individuals. The Bay Circuit Alliance is led by the Appalachian Mountain Club which is working to implement 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 the trail’s 230+ miles.