Mariposa County is a county in California, located in the western foothills of the Sierra Nevada mountains. The county seat is Mariposa. The county's eastern half is the central portion of Yosemite National Park. Mariposa County was created in 1850 and took its name from Mariposa Creek, which named by Spanish explorers in 1806, when they discovered great clusters of butterflies ("mariposas" in Spanish) in the foothills of the Sierras. For many years, residents marked the annual arrival (in May) of migrating Monarch butterflies with a "Butterfly Days" parade. The county has a total area of 1,463 miČ, 99.9% of it is land and 0.1% of it is water.