Southern California, or So Cal, is defined as the southern portion of the U.S. state of California. Its population centers on the counties of Los Angeles, Orange, San Diego, San Bernardino, Riverside and Ventura. The region is home to over 23 million people and is the nation’s second most populated region, behind only the BosWash Region in the Northeastern United States.
There is no official definition for the northern boundary of Southern California. However, most definitions in use include all the land south of the Tehachapi Mountains, located about 70 miles (113 km) north of Los Angeles.
On the west of Southern California lies the Pacific Ocean; to the south is the international border between the United States and Mexico; to the east are the Mojave and Colorado Deserts and the Colorado River at the state’s border with Arizona and Nevada. Southern California is also divided into the Coastal Region (Orange County, Los Angeles County, San Diego County, Santa Barbara County, and Ventura County) and the larger, more sparsely populated, desert Inland Empire (San Bernardino County, Riverside County, and Imperial County). The division between the Coastal Regions and the Inland Empire winds along the backs of the coastal mountain ranges such as the Santa Ana Mountains. A related geographical term is cismontane Southern California, which refers to the portion of California on the coastal side of the Transverse and Peninsular mountain ranges. The term "Southern California" often refers to this region specifically, as opposed to largely desert areas comprising the rest of the southern portion of the state, which are referred to as transmontane Southern California.
San Diego (pronounced /ˌsændiˈeɪgoʊ/) is a coastal Southern California city located in the southwestern corner of the continental United States. In 2007, the city’s population was estimated to be 1,266,731. It is the second largest city in California and the eighth largest city in the United States, by population. It is the county seat of San Diego County. and is the economic center of the San Diego–Carlsbad–San Marcos metropolitan area, the 17th-largest in the United States with a population of 3,146,274 as of 2008, and the 21st-largest metropolitan area in the Americas when including Tijuana (See San Diego-Tijuana Metro.).
San Diego County lies just north of the Mexican border—sharing a border with Tijuana—and lies south of Orange County. It is home to miles of beaches, a mild Mediterranean climate and 16 military facilities hosting the United States Navy, the United States Coast Guard and the United States Marine Corps.
The presence of the University of California, San Diego (UCSD) with the affiliated UCSD Medical Center promotes research in biotechnology. San Diego’s economy is largely composed of agriculture, biotechnology/biosciences, computer sciences, electronics manufacturing, defense-related manufacturing, financial and business services, ship-repair and construction, software development, telecommunications, and tourism. The city of San Diego itself has deep canyons separating its mesas, creating small pockets of natural parkland scattered throughout the city. The same canyons give parts of the city a highly segmented feel, creating literal gaps between otherwise proximal neighborhoods and contributing to a low-density, car-centered built environment. Downtown San Diego is located on San Diego Bay. Balboa Park lies on a mesa to the northeast. It is surrounded by several dense urban communities and abruptly ends in Hillcrest to the north. The Coronado and Point Loma peninsulas separate San Diego Bay from the ocean. Ocean Beach is on the west side of Point Loma. Mission Beach and Pacific Beach lie between the ocean and Mission Bay, a man-made aquatic park. La Jolla, an affluent community, lies north of Pacific Beach. Mount Soledad in La Jolla offers views from northern San Diego County to Mexico. Mountains rise to the east of the city, and beyond the mountains are desert areas. Cleveland National Forest is a half-hour drive from downtown San Diego. Numerous farms are found in the valleys northeast and southeast of the city. San Diego County has one of the highest counts of animal and plant species that appear on the endangered species list among counties in the United States.