Anza-Borrego Desert State Park (ABDSP) is a state park located within the Colorado Desert of southern California, United States. The park takes its name from 18th century Spanish explorer Juan Bautista de Anza and borrego, the Spanish word for bighorn sheep. With 600,000 acres (240,000 ha) that includes one-fifth of San Diego County, ABDSP is the largest state park in California and, after New York's Adirondack Park, the second largest in the contiguous United States. The park occupies eastern San Diego County and reaches into Imperial and Riverside counties, enveloping two communities: Borrego Springs (home of the park headquarters) and Shelter Valley.