"Mystic River Bridge" redirects here. For the bridge in Mystic, Connecticut, see Mystic River Bascule Bridge.The Maurice J. Tobin Memorial Bridge (formerly and still sometimes referred to as the Mystic River Bridge or less often the Mystic/Tobin Bridge) is a cantilever truss bridge that spans more than two miles (3 km) from Boston to Chelsea over the Mystic River in Massachusetts. The bridge is the largest in New England.