Morris Dam is a concrete gravity dam across the San Gabriel River in the U.S. state of California. It impounds Morris Reservoir, directly downstream of San Gabriel Dam. The dam was built in the 1930s as a water supply facility for the city of Pasadena, but is now mostly utilized for flood control and flow regulation for groundwater recharge. Situated in northern Lo…Morris Dam is a concrete gravity dam across the San Gabriel River in the U.S. state of California. It impounds Morris Reservoir, directly downstream of San Gabriel Dam. The dam was built in the 1930s as a water supply facility for the city of Pasadena, but is now mostly utilized for flood control and flow regulation for groundwater recharge. Situated in northern Los Angeles County, the dam impounds the 417-acre Morris Reservoir in the Angeles National Forest, a few miles northeast of Azusa. From the 1940s to the 1990s, the reservoir was also used for underwater missile testing by the United States military.