Construction on the reservoir began in 1933, at the same time the aqueduct was being built across the desert. The reservoir site had previously been occupied chiefly by carob orchards and tin mines. Lawrence Holmes, Sr., who owned 1,100 acres in the future reservoir basin, lost his property to eminent domain in a lengthy court battle. The dam across Cajalco Canyon and its intake structure were completed in 1939. The first water arrived from the Colorado River in February 1940, and water deliveries began in 1941. In 1961, the reservoir's capacity was nearly doubled to its current capacity of 182,000 acre-feet.