High Quality Content by WIKIPEDIA articles! Caltrain is a commuter rail transit system that serves the San Francisco Peninsula and the Santa Clara Valley in the U.S. state of California. It is operated under contract by Amtrak and funded jointly by the City and County of San Francisco, San Mateo County Transit District (SamTrans), and Santa Clara Valley Transportation Authority (VTA) through the Peninsula Corridor Joint Powers Board (PCJPB). The system serves over 36,993 passengers a day as of the fiscal year 2008.