Throwback Thursday: Key System and other forgotten Bay Area rail

Trains on the Bay Bridge? A streetcar rolling down Sloat Boulevard in San Francisco? Rails out to the Cliff House? 

It's all true and well documented at Chris Arvin's site The Bay Area's Lost Streetcars. The site has dozens of maps and a treasure trove of photos.

Perhaps the best known "lost" rail in the ever evolving world of Bay Area transportation is the Key System, which traversed the Bay Bridge for almost two decades before it was removed. 

The Key System served the East Bay with rail and buses for decades before the Bay Bridge opened in 1936. When the span opened, rails were placed along the lower deck, taking commuters into San Francisco. 

But dwindling ridership and the rise of the automobile helped kill off the Key System. Voters created the Alameda-Contra Costa Transit District (AC Transit) in 1956, and the district eventually bought out the Key System.

Dozens of other rails also fell by the wayside over the years, often in deference to the automobile. But as traffic piled up, planners looked back to rail and BART was born.