The NWP narrow-gauge line was built as the North Pacific Coast Railroad in 1873 from a San Francisco ferry connection at Sausalito to the Russian River at Monte Rio. Rails were extended downriver to Duncans Mills in 1876, and up Austin Creek to Cazadero in 1886. This narrow-gauge line became the Shore Division of the NWP formed by Santa Fe and Southern Pacific in 1907. Freight traffic was heavy as the lower Russian River valley was a major source of redwood lumber for rebuilding San Francisco after the 1906 San Francisco earthquake. The NWP narrow-gauge obtained additional freight cars from the South Pacific Coast Railroad (SPC) as the SPC was converted to standard gauge between 1907 and 1909. Ferries "Lagunitas", "Ukiah", and "Sausalito" carried narrow-gauge freight cars across San Francisco Bay from Sausalito to the dual-gauge San Francisco Belt Railroad.