Mudhills created by centuries of erosion. Anza-Borrego Desert State Park (Est. May 1948), largest state park in California 600,000 acres (2,400 km2); second-largest in continental US. Five hundred miles of dirt roads, 12 wilderness areas. Park named for Spanish explorer Juan Bautista de Anza and the Spanish word borrego, or bighorn sheep. San Diego County, CA.