The Great San Francisco Earthquake and Fire of 1906 destroyed the bridge that the South Pacific Coast Railroad used to cross San Leandro Bay east to Encinal Avenue. It also made the tracks that ran along today’s Main Street on the West End unusable. 

Five years later, Southern Pacific Railroad’s (SP) began running the East Bay Electric Line.  American Car & Foundry supplied the all-electric system with 40 powered passenger coaches, referred to as “motors”; 50 unpowered passenger coaches, called “trailers”; and 20 powered combination passenger-baggage coaches or “combos”; all painted in Pullman Green and sporting square front windows. 

In 1912 SP painted the cars red and replaced the square front windows with round ones. The public began called them “Big Reds.”

In 1924 St. Louis Motor Cars supplied six more “motors.” In 1934, SP established the Interurban Electric Railway (IER) in 1934. Four year later on Nov. 30, 1938, the IER took over the East Bay Electric Lines and began operating motor cars over the Bay Bridge to the San Francisco Transbay Terminal on January 15, 1939.

When the motor cars began running across the Bay Bridge, SP installed round numbered disks on the front and back of the motor cars. In Alameda, the No. 4 showed on the front of the cars as they ran counterclockwise—east on Lincoln Avenue and west on Encinal Avenue around Alameda. The No. 6 showed on the front as they ran clockwise west on Lincoln and east on Encinal. 

The Big Reds stopped running in July 1941.