From the Historic American Engineering Record (HAER, MA 13-BOST-136)
“The Chelsea Street Bridge is significant as an example of a bascule bridge, a type of moveable bridge developed in the early 20th century and widely adopted in subsequent years for both railway and highway spans. The Strauss heel trunnion bascule was one of four bascule designs developed by Strauss and may be the only Strauss heel trunnion bascule bridge in Massachusetts.
“It is the only one in Boston. The Chelsea Street Bridge is also one of the few surviving drawbridges in Boston Harbor. Ofthe 14 draw bridges in operation in 1940, only nine remain and only two, the Meridian Street Bridge and the Chelsea Street Bridge, both over the Chelsea River, are still operational.”EastBostonDocument-ma1599data