 The dam is built in a part of the Santa Ynez River called the "Gibraltar Narrows" that gave its name to the Gibraltar (or Sunbird) mercury mine, which operated next to what is now Gibraltar Reservoir between the 1870s and 1990s.Gibraltar Dam is a constant radius concrete arch dam high and long.The dam is located about from the mouth of the Santa Ynez River and just above the confluence of Devils Canyon with the river.