The combined peak population of the Poston camps was over 17,000, mostly from Southern California. At the time Poston was the third largest "city" in Arizona. It was built by Del Webb, who would later become famous building Sun City, Arizona and other retirement communities. The Poston facility was named after Charles Debrille Poston, a government engineer who established the Colorado River Reservation in 1865 and planned an irrigation system to serve the needs of the Indian people who would live there.