This is the site of the oldest transportation route across the Willamette River (a ferry, 1855) and Portland's first bridge across the Willamette. The original Morrison Bridge (1887) was replaced by a swing-span (1905), but this was deemed unfriendly to both maritime and auto traffic.
Though the "new" Morrison Bridge is the least visually interesting of the five downtown bridges, it is very car-friendly, allowing for six lanes of traffic. It was designed with open metal grating to reduce its weight and allow rain runoff. The bridge has two huge 950-ton concrete counterweights in its main piers, which raise the bridge to an angle of 73 degrees, allowing maritime traffic to pass beneath it. These weights qualify the Morrison as Oregon's largest mechanical structure. (Reread that last sentence to fully appreciate its magnitude.) They also define the span as a bascule (French for "seesaw") bridge.
* The Morrison Bridge's east control tower has no controls. It's just there for looks.