Gibraltar Dam, Arch dam in Santa Barbara County, United States

Gibraltar Dam is a constant-radius concrete arch dam 194.5 feet (59.3 m) high and 600 feet (180 m) long, built across the Gibraltar Narrows of the Santa Ynez River just above the confluence of Devils Canyon. Its concrete spillway runs south from the main dam, controlled by four manually operated radial gates, and overflow cascades down the natural sandstone face beside it as a 150-foot waterfall.

Construction started in 1913 and finished in 1920, making it the first structure built to control the Santa Ynez River's flow. The project arose from the region's growing need for a reliable water supply.

The name comes from the Gibraltar Narrows, the river gorge where the dam stands, which also gave its name to the Gibraltar (Sunbird) mercury mine. That mine operated beside today's reservoir from the 1870s until the 1990s.

The dam is visible from public roads but sits in a mountain area requiring a drive inland to reach. Visitors should know that access may be limited depending on the season and weather conditions.

The spillway is built so that overflow cascades down the natural sandstone face beside the dam, forming a waterfall about 150 feet (46 m) high. Four manually operated radial gates control the spillway, and flashboards can be added in the non-flood season to raise storage.