After 17 years of petitioning by residents of Ferndale and the Eel River valley , Humboldt County Supervisors accepted bids for construction in 1910 , and work started March 20 of that year . Reinforced concrete was used because studies after the 1906 San Francisco earthquake along of the San Andreas Fault from Ferndale south to San Jose , California showed that reinforced concrete withstood earthquakes . The nearly span cost to build , and consumed millions of board feet of local redwood timber for the framing . Construction was finished and the bridge put into operation on November 8 , 1911 . As completed , the bridge had wooden trestle approach spans and long . The reinforced concrete structure was long overall with a wide roadway carried on seven long arches . The original wooden approaches were replaced with the current concrete ramps in 1920
1906 San Francisco earthquake
1906 San Francisco earthquake
Fernbridge (bridge)