 Construction began in National City, just south of San Diego, in 1881, and proceeded northward to the present day city of Oceanside.From there, the line turned to the northeast through Temecula Canyon, then on to the present cities of Lake Elsinore, Perris and Riverside before a connection to the Southern Pacific Railroad (SP) in Colton.Following a frog war where the SP refused to let the California Southern cross its tracks, a dispute that was resolved by court order in favor of the California Southern, construction continued northward through Cajon Pass to the present day cities of Victorville and Barstow.