LA River: Sixth St / Whittier Blvd bridge 1826a

Sixth Street/Whitier Blvd bridge over the Los Angeles river. Built in 1932, it's a very long bridge (3500') spanning the LA river, various local streets, multiple railroad tracks, and two freeways that were built many years after the bridge (the I-5 and the 101). It has an unusual problem with the concrete that makes it vulnerable to collapsing in an earthquake.

None of the other bridges across the LA river have a steel truss section. I didn't find any explanation as to why this bridge does.