[wburg]

Note the tracks on the Tower Bridge, and the wires above the camera in the second and last photo. When it was built, those tracks carried the Sacramento Northern Railway, an electric interurban railroad. SN carried both freight and passengers, running from Chico to Oakland (the longest electric interurban in the country) with Sacramento as the system's hub. Passenger trains ran down M Street and turned north at 8th, freight trains turned south on Front Street. They served the waterfront transfer sheds, where goods were moved between barges and riverboats and 4 different railroads operating on Front Street (SN, Southern Pacific, Western Pacific, and Central California Traction, another interurban that ran to Stockton.) There were more jobs on the other side of Front Street: rice mills, canneries, ironworks, transfer and freight houses, lumberyards, oil depots, gasworks, and other factories. There were more docks along the river north of the Tower Bridge, operated by Southern Pacific (you can see them in the second to last photo) and more industrial facilities north of the I Street Bridge, including Pioneer Mills, a lumber mill, and the PG&E powerhouse. The mighty Southern Pacific shops were just inland from there, building steam locomotives and other heavy equipment for the railroad.

The Art Deco "The River Lines" building is where passengers boarded and disembarked the Delta King and Delta Queen, which operated between San Francisco and Sacramento until 1940. Before the M Street Bridge was built, the interurban line (then called Northern Electric) trains stopped at the foot of M Street so passengers from Chico to Sacramento could transfer to the River Lines dock to continue to San Francisco. After the M Street bridge, electric trains could continue to Woodland, and through a deal with another railroad, the Oakland Antioch & Eastern, to Oakland. NE and OA&E later merged into Sacramento Northern.

Passenger trains stopped in 1940-41, and the bridge was de-electrified in 1953, but there were still diesel freight trains crossing the Tower Bridge until the early 1960s.