"The single-leaf, thru-plate girder Strauss trunnion bridge is one of three Strauss bascules built in 1911 by the Boston and Maine Railroad on its eastern route (others at Annisquam River in Gloucester and the longest of the three across the Saugus River in Lynn). It is a well-preserved and complete example of one of the earliest types of movable bridges and is representative of the Strauss innovation of locating the pivoting counterweight in a frame over the short arm thus eliminating the need for an expensive pit. Strauss also popularized the use of concrete for the counterweight and patented the multi-trunnion bearing bridge with its distinctive overhead, parallelogram counterwieght frame with a pivoting counterweight. The riveted, built-up girder itself is shaped to follow its bending moment curve during operation and the segmental rack, is original as are the riveted knees, floor beams, and lateral bracing. Modifications to the span are limited to longitudinal and transverse angle braces to counteract the sway of the moving counterwight and bolted on, electrically operated toe locks added in 1988. The original geared drive mechanism was replaced by a sealed unit (motor and reduction gears), fixed pinion, and welded segmental rack in 1987-88. While the back wall of the toe is concrete, the back wall is the original/early ashlar block held together at the top with iron staples. A corrugated sheet wall and concrete pad were installed under the bridge to accommodate the sealed unit. Despite the replacement of the original operating mechanism, the span itself is very well preserved and is an important example of early-20th century, patented, movable bridge technology. It is one of only two overhead Strauss trunnions on the MBTA system."
-Mary E. McCahon, MBTA Historical Property Survey Phase II, 10/1988