Santa Rosa and San Jacinto Mountains National Monument, National monument in Riverside County, United States

Santa Rosa and San Jacinto Mountains National Monument covers 280,071 acres (113,341 ha) of the Peninsular Ranges, the northernmost mountains of that system, west of the Coachella Valley in Riverside County. Terrain climbs from below sea level to San Jacinto Peak at nearly 11,000 feet (3,400 m), one of North America's steepest fault-block escarpments. Desert scrub covers more than 160,000 acres of alluvial fans, giving way to montane coniferous forest between about 5,500 and 9,000 feet.

Congress created the monument in October 2000 under Public Law 106-351, covering 280,071 acres. Protection began earlier: forest reserves from the late 19th century, San Bernardino National Forest in 1925, Mount San Jacinto State Park in 1928, and the San Jacinto Wilderness after the 1964 Wilderness Act. The Santa Rosa Wilderness was added in 1984.

The Cahuilla have lived in these mountains for at least 3,000 years, ancestors of today's Agua Caliente band, building villages at canyon mouths and sometimes separate summer and winter settlements. Petroglyphs, pit houses and stone-building foundations remain, and several peaks are held sacred. The Martinez Canyon Rockhouse is listed on the National Register of Historic Places.

The visitor center at Highway 74 in Palm Desert offers information and orientation for exploring the area and provides access to the Ed Hastey Garden Trail. The best time to visit is outside the extreme summer heat, when conditions are more comfortable for outdoor activities.

The area contains the largest system of native fan palm oases in the United States. These rare oases form where the Palm Canyon Fault creates surface water sources, allowing ecosystems to flourish in this otherwise dry region.