Joshua Tree National Park is located in southeastern California. Declared a U.S. National Park in 1994 when the US Congress passed the California Desert Protection Act (Public Law 103-433), it had previously been a U.S. National Monument since 1936. It includes over 1,234 mi² (3,196 km²) of land. A large part of the park is designated to wilderness area; some 914 mi² (2,367 km²). Straddling the San Bernardino County/Riverside County border, the park includes parts of two deserts, each an ecosystem whose characteristics are determined primarily by elevation. Below 3,000 feet (900 m), the Colorado Desert encompasses the eastern part of the park and features natural gardens of creosote bush, ocotillo, and cholla cactus. The Little San Bernardino Mountains run through the southwest edge of the park.