San Mateo Rocks

San Mateo Rocks are uninhabited islands that lie approximately 0.5 mi (0.80 km) off the coast of California,^[1] to the south of San Clemente, and just north of San Mateo Point, a minor headland that marks the border between Orange County and San Diego County.^[2] The rocks rise about 3 ft (or about 1 m) above high tide.^[3] In 2017 the San Mateo Rocks, a pinniped haul-out and scuba destination, became part of the California Coastal National Monument.^[4][5]

The Rocks first appear in the documentary record of the area in 1889, when they were described in the Coast Pilot.^[3] The sloop Victoria wrecked on the rocks in a storm in 1907.^[6] In 1931 the United States Coast Guard reserved the location (along with several other Orange County Rocks) for a possible future San Mateo Rocks Lighthouse, and an act of Congress assigned ownership to the Bureau of Land Management in 1935,^[7] but the lighthouse facility was never built.^[5][4] In the early 1970s the waters around the rocks were a collection site for seaweed species in genus Gelidium for use in agar production.^[8]

The rocks host a transient population of California sea lions.^[9][10] Indigenous people may have used San Mateo Rocks as a pinniped hunting ground.^[11] On one occasion this population of sea lions attracted a pod of orcas—quite uncommon in local waters—who used a clever pack-hunting technique to force the sea lions off the rock and into the water where they would be ready prey.^[12] The rocks are a common destination for local dive boats.^[13]