Big Dalton Dam, Flood control dam in Los Angeles County, United States.

Big Dalton Dam is a multiple-arch concrete dam with a double-wall buttress design by engineer Fred A. Noetzli, completed in August 1929. It stands in Big Dalton Canyon, about 4 miles northeast of Glendora in the San Gabriel Mountains, and impounds 991 acre-feet (1.2 million cubic meters) of water.

Built by the Los Angeles County Flood Control District between 1927 and 1929, Big Dalton Dam was completed in August 1929. It is one of the earliest multiple arch "double-wall" buttress dams designed by engineer Fred A. Noetzli. The county built it to hold back floodwater from Big Dalton Canyon and to store water; the Los Angeles County Department of Public Works runs it today.

The facility represents California's early twentieth-century infrastructure development during a period of rapid population growth and urban expansion. It shows how communities worked to protect their settlements from natural hazards.

Visitors can observe the dam structure from designated viewing areas accessible through nearby roads. The best time to visit is typically during dry weather when access roads are in good condition.

The dam is one of the earliest examples of Fred A. Noetzli's multiple arch "double-wall" buttress design, and its documentation is held in the Historic American Engineering Record as HAER No. CA-227, with 23 photographs, 4 data pages and 3 caption pages. A separate record, HAER No. CA-227-A, covers the dam's Shelter House.