The county experienced a period of migration of "Okies" from drought-trodden dust bowl farms by the need of migrant labor, and prosperous job-seekers alike from across the U.S. arrived in the 1930s and 1940s, especially in World War II and after the completion of the All American Canal from its source, the Colorado River, from 1948 to 1951. By the 1950 census, over 50,000 residents lived in Imperial County alone, about 40 times that of 1910. Most of the population was year-round but would increase every winter by migrant laborers from Mexico. Until the 1960s, the farms in Imperial County provided substantial economic returns to the company and the valley.