Natural Bridges State Beach is a California state park in Santa Cruz, California, in the United States. The park features a natural bridge across a section of the beach. It is also well known as a hotspot to see monarch butterfly migrations. The Monarch Butterfly Natural Preserve is home to up to 150,000 monarch butterflies from October through early February. History The first inhabitants in the Santa Cruz area were small groups of Native Americans. The Ohlone were a semi-nomadic tribe that hunted game and marine mammals and supplemented their diets with shellfish, fish, edible roots and shoots, acorns, nuts, and seeds. The Ohlone raised medicinal plants and herbs. They made tools from locally found stones and shells. Their crafts included shellfish jewelry and baskets. The displacement of the natives began with the Spanish colonization of the Americas when missionaries and soldiers brought the Ohlone into the missions. The population of Native Americans was greatly reduced by European diseases to which they had no resistance. Governance of the area was transferred from Spain to Mexico after the Mexican War of Independence. The citizens of Mexico used what is now Natural Bridges State Beach as pasture land for their cattle. California became part of the United States after the Mexican–American War. The area in and around the park later supported a dairy farm, a brussels sprouts farm, hotel, housing for mill workers, a South Seas movie set and a failed housing development. The land was purchased by the State of California in 1933 and construction of the state beach facilities began in 1954. The land surrounding the park was largely wild and undeveloped until the 1970s. The park is now surrounded by beach development and commercial properties. Geology Natural Bridges State Beach is named for the naturally occurring mudstone bridges that were carved by the Pacific Ocean into cliffs that jutted out into the sea. The arches formed over a million years ago when a combination of silt, clay and diatoms were solidified into a mixture of stone that formed the three original arches of the beach. Wave erosion carved the arches and then cut away the cliffs leaving only islands. Of the three original arches only the middle one remains. The outermost arch fell sometime in 1905 or 1906, and the inner arch collapsed during a storm on the night of January 10, 1980. The middle arch is in danger