OK, I'm falling further behind, I'll try to get caught up. This week's bridge is the Third Avenue Bridge over the Harlem River between The Bronx and The Manhattan.
The bridge is a swing drawbridge with a 300-foot span that swings open to allow two 102-foot wide channels. When closed, it gives 25 feet of clearance above the water. It has a 52-foot wide roadway that carries four lanes of southbound traffic into Manhattan and a 9-foot wide sidewalk on each side, although the sidewalk on the southwest side is currently closed. The total length is 2,800 feet.
A bridge on the site was proposed as far back as 1770 to carry the new Boston Post Road (which in the Southern Bronx is now Third Avenue), which would be a major link between New York and New England. A dam/bridge, the Coles Bridge, was finally built by John B. Coles in 1797. A new cast-and-wrought iron swing bridge was opened on the site in 1868. Construction on the third and current bridge began in 1893 in conjunction with the dredging and engineering of the Harlem River Ship Canal. The bridge opened in 1898 to vehicular and trolley traffic, and the sidewalks were opened in 1901. Trolley service was discontinued in 1953 when the bridge underwent rehabilitation and the Third Avenue Elevated in the Bronx was torn down. A new span was placed on the existing foundation structures in 2004-2005.
As near as I can tell, Third Avenue (not 3rd Avenue) in the Bronx is a continuation of 3rd Ave. in Manhattan (Manhattan street signs read "3 Ave", in Bronx, "Third Ave"). There is no north-south numbered avenue system in the Bronx. In Manhattan it conforms to the street grid and runs in a straight line, but in the Bronx it meanders around quite a bit before ending at Fordham Road. As I said, the southern portion was originally part of Boston Post Road. What is now named Boston Road (and eventually Boston Post Road) begins by branching off Third Ave. to the northeast just north of E. 163rd St. in Morrisania.
The sidewalk across the bridge can be reached in Manhattan from Harlem River Park in Harlem, most directly from a pedestrian bridge over an offramp (stairs to climb and descend) at E. 129th St. and Lexington Ave. In the Bronx, the sidewalk begins in the Mott Haven neighborhood on Third Ave. just south of 135th St. and the elevated Major Deegan Expressway, but there is also a staircase with access a couple of blocks south on Third Ave. at the western end of Bruckner Boulevard. There are no major specific attractions in the immediate area on either side of the bridge, although you are in the middle of "Bridge Row", a series of six bridges (plus a railroad bridge) over the Harlem River from the Triboro Bridge to the Macombs Dam Bridge (from 125th St. to 155th St. in Manhattan).