In the first half of the 20th century, the San Francisco Bay Area built out and subsequently dismantled a comprehensive mass transit system. It was mostly electric, serving commuters from outlying regions to access the cities of San Francisco and Oakland. Its right-of-ways were either given to BART or turned into expressways and roads.
The San Francisco Area Key System was a privately-owned commuter transportation system in the East Bay that ran from 1903 to 1958. A news report from the 1980s describes its demise at the hands of auto-makers and petroleum interests. There’s even a site that memorializes The Bay Area’s Lost Streetcars.
The Peninsular Railway was a subsidiary of Southern Pacific Railroad and ran along the Peninsula from 1900 to 1934.
Tracks, Tires, & Wires catalogues the old transportation system, but I can’t find any copies to read.
The Caltrain HSR Compatibility blog wrote an article in May 2020 about how much the Southern Pacific Railroad Commuter System paid its staff.