The tracks for the San Ramon Branch Line of the Southern Pacific Railroad were laid down and completed in 1891. The line extended from San Ramon to an unincorporated area known as Avon, east of Martinez, where it connected to the Oakland/Stockton Line. On February 7, 1909, Southern Pacific extended the line south to Radum (near Pleasanton). In 1934, passenger service ended. By 1986, Contra Costa County had obtained the railroad right-of-way and the Iron Horse Regional Trail was established along its path.