The Bay Bridge combines suspension, cantilever, tunnel, and truss constructions in an astonishing 8.4-mile-long structure. Envisioned first in 1872 by the legendary Emperor Norton, the project finally coalesced in the 1920s, although initial studies concluded that the bridge could not be built due to the bay's deep muddy waters and the area's strong earthquakes. President Herbert Hoover, who was also an engineer, took up the cause, and the $80.8-million...