Image: United States Bureau of Reclamation photo from Library of Congress
1939 view of the Imperial Dam at the headwaters of the All-American Canal. The dam was completed in 1938 and the first water was delivered in 1940.
Excerpt from https://www.usbr.gov/projects/index.php?id=514:
The All-American Canal System, located in the southeastern corner of California, consists of the Imperial Diversion Dam and Desilting Works, the 80-mile All-American Canal, the 123-mile Coachella Canal, and appurtenant structures. The system has the capacity, through water diversions from the Colorado River at Imperial Dam, to irrigate about 530,000 acres of fertile land in the Imperial Valley and about 78,530 acres in the Coachella Valley.