The purpose of the mole was to extend tracks of rail-based transportation lines beyond the shallow mud flats along the shore of the East Bay into water deep enough to accommodate the passenger and rail ferries to San Francisco.

A Southern Pacific Railroad passenger train headed for Oakland fell into the estuary after failing to stop for the open drawbridge at Webster Street.

Southern Pacific's electrified trains were not streetcars, but full-sized railroad cars which connected to the mainland by bridges at Webster Street and Fruitvale.

[6] In the 1930s Pan American Airways established a seaplane port along the fill that led to the Alameda Mole.

This major Naval facility included a large airfield and docks for several aircraft carriers.