Pico Rivera was founded in 1958, from the merger of the long-standing unincorporated communities of Pico (named for Pío Pico, the last Mexican governor of California) and Rivera (the Spanish word for "riverbank"). Situated on a rich alluvial plain between the Rio Hondo and the San Gabriel River, the area was once predominantly agricultural; but, at the end of WWII, the fast rising demand for homes lured builders to the attractive terrain. Since the 1950s, it has been both residential as well as industrial. It had a Ford Motor Company plant for many years: Los Angeles Assembly. Pico Rivera lies below the Whittier Narrows, making it one of the "Gateway Cities".