In the late 1800s both the Southern Pacific Railroad ( “ SP ” ) and the Atchison , Topeka and Santa Fe Railway ( “ AT&SF ” ) had great interests in building lines north from San Francisco to Humboldt County to transport lumber south . The Southern Pacific Railroad controlled the southern end of the line from Willits south to Marin and Schellville , while the AT&SF controlled line south from Eureka through Humboldt County . Both railroads planned to build a line north , the AT&SF starting with a boat connection in present-day Larkspur , California , and the Southern Pacific , starting at its interchange in American Canyon , north through Napa , Sonoma , Mendocino and Humboldt counties to finally terminate in Eureka , California . As plans went forward it became clear that only one railroad would be profitable serving Mendocino and Humboldt Counties , so the Southern Pacific and Santa Fe entered into a joint agreement , and in 1906 merged 42 railroad companies between Marin and Humboldt Bay to create one railroad line stretching from Sausalito to Eureka . Completion of the project was disrupted by the 1906 San Francisco earthquake ; plans and right-of-way documents were destroyed in the subsequent fire . After a time-expedient " punt " of the route through the unstable Eel River Canyon , construction was finally completed in October 1914 when a " golden spike " ceremony and celebration was held to mark the accomplishment . There were also dozens of miles of narrow-gauge trackage in Marin and Sonoma Counties
1906 San Francisco earthquake
1906 San Francisco earthquake
Northwestern Pacific Railroad