The lines were the first third-rail electrification in California, and the first major railroad to use alternating current signals.

)[1]: 71  Revenue service began between Sausalito and Mill Valley on August 21, 1903, and to San Rafael on October 17.

[1]: 71  The common control allowed expansion: a cutoff was built east from Baltimore Park in Corte Madera to the CNW line, which was then electrified from there to San Rafael.

[1]: 72  Under NWP control, the ex-North Shore main line was electrified from San Anselmo to Manor in 1908.

The 1937 opening of the Golden Gate Bridge, which made automobile commuting from Marin County to San Francisco possible without using ferries, deeply hurt the interurban operations.

[1]: 74 [2] The only remaining passenger service on the NWP was a small number of trains between Tiburon and points north.

[4] Former interurban stations at Mill Valley, Larkspur, B Street, and San Rafael remain extant, as does the Baltimore Park substation.