San Bernardino Mountains in the context of "San Gorgonio Pass"

The Inland Empire (commonly abbreviated as the IE) is a metropolitan area and region inland of and adjacent to coastal Southern California in the Greater Los Angeles area, focusing around the cities in Riverside and San Bernardino county with Los Angeles County and Orange County to the west. The region, at its narrowest definition, includes the cities of northwestern Riverside County and southwestern San Bernardino County that are part of the contiguous urbanized area of Greater Los Angeles. It is sometimes considered to include the desert communities of the Coachella and Victor Valleys, respectively on the other sides of the San Gorgonio Pass and San Bernardino Mountains from the Santa Ana River watershed that creates the majority of the Inland Empire. A much wider definition includes the entireties of Riverside and San Bernardino counties, stretching east to the Nevada and Arizona borders and covering a larger area than West Virginia; this definition is primarily used by the US Census Bureau, which exclusively delineates metropolitan areas at the county level.

The U.S. Census Bureau–defined Riverside–San Bernardino–Ontario metropolitan area, which comprises Riverside County and San Bernardino, California, covers more than 27,000 sq mi (70,000 km) and had a population of about 4.6 million in 2020. At the end of the 19th century, the Inland Empire was a major center of agriculture, including citrus, dairy and winemaking. Agriculture declined through the 20th century and a rapidly increasing population, helped by families migrating in search of affordable housing, has led to more residential, industrial and commercial development since the 1970s.

Fire ecology is a scientific discipline concerned with the effects of fire on natural ecosystems. Many ecosystems, particularly prairie, savanna, chaparral and coniferous forests, have evolved with fire as an essential contributor to habitat vitality and renewal. Many plant species in fire-affected environments use fire to germinate, establish, or to reproduce. Wildfire suppression not only endangers these species, but also the animals that depend upon them.

Wildfire suppression campaigns in the United States have historically molded public opinion to believe that wildfires are harmful to nature. Ecological research has shown, however, that fire is an integral component in the function and biodiversity of many natural habitats, and that the organisms within these communities have adapted to withstand, and even to exploit, natural wildfire. More generally, fire is now regarded as a 'natural disturbance', similar to flooding, windstorms, and landslides, that has driven the evolution of species and controls the characteristics of ecosystems.

San Gorgonio Mountain, also known locally as Mount San Gorgonio, or Old Greyback, is the highest peak in Southern California and the Transverse Ranges at 11,503 feet (3,506 m).

It is in the San Bernardino Mountains, 27 miles (43 km) east of the city of San Bernardino and 12 miles (19 km) north-northeast of San Gorgonio Pass. It lies within the San Gorgonio Wilderness, part of the Sand to Snow National Monument managed by the San Bernardino National Forest.

The Coachella Valley (/koʊˈtʃɛlə, ˌkoʊ.ə-/ koh-CHEL-ə, KOH-ə-) is an arid rift valley in the Colorado Desert of Southern California in Riverside County. The valley has been referred to as Greater Palm Springs and occasionally the Palm Springs Area due to the historic prominence of the city of Palm Springs. The valley extends approximately 45 mi (72 km) southeast from the San Gorgonio Pass to the northern shore of the Salton Sea and the neighboring Imperial Valley, and is approximately 15 mi (24 km) wide along most of its length. It is bounded on the northeast by the San Bernardino and Little San Bernardino Mountains, and on the southwest by the San Jacinto and Santa Rosa Mountains.

The Coachella Valley is notable as the location of several wintertime resort cities that have become popular destinations for full time retirees and seasonal residents known as snowbirds. The valley is also known for a number of annual events, including the Coachella Valley Music and Arts Festival, the Stagecoach Country Music Festival, and the Riverside County Fair and National Date Festival, all held in Indio. Other events include the Palm Springs Modernism Week, Palm Springs International Film Festival, the ANA Inspiration and Desert Classic golf tournaments, and the Indian Wells Open tennis tournament.

The Santa Ana River is the largest river entirely within Southern California in the United States. It rises in the San Bernardino Mountains and flows for most of its length through San Bernardino and Riverside counties, before cutting through the northern Santa Ana Mountains via Santa Ana Canyon and flowing southwest through urban Orange County to drain into the Pacific Ocean. The Santa Ana River is 96 miles (154 km) long, and its drainage basin is 2,650 square miles (6,900 km) in size.

The Santa Ana drainage basin has a diversity of terrain, ranging from high peaks of inland mountains in the north and east, to the hot, dry interior and semidesert basins of the Inland Empire, to the flat coastal plain of Orange County. Although it includes areas of alpine and highland forest, the majority of the watershed consists of arid desert and chaparral environments. Due to low regional rainfall, the river carries only a small flow except during the brief winter season, when it is prone to massive flash floods. The San Jacinto River, which drains the southern half of the watershed, rarely reaches the Santa Ana except in extremely wet years. A wide variety of animal and plant communities depend on the riparian zones and remnant wetlands along the Santa Ana River.