Southern California, sometimes abbreviated SoCal, is an informal name for the southern one-third of the state of California. There are no clear, exact boundaries for this area; instead, residents rely on physical features to establish the boundary. On the west is the Pacific Ocean; to the south is the international border between the United States and Mexico; and to the east is the state border between California and Arizona. The north boundary is more difficult to define. One generally accepted 'physical' boundary between Southern California and the rest of the state is the Tehachapi Mountain range located about 100 miles north of Los Angeles . Another useful boundary is the San Gabriel Mountain range located about 10 miles north of downtown Los Angeles. Note that depending on which of the two mountain ranges is used for the northern boundary of the region, different communities/cities and counties will be included in, or excluded from, the area called "Southern California". Using the San Gabriel Mountain range as the boundary, politically the following six counties (in descending order of population) are included: Los Angeles, Orange, San Diego, San Bernardino, Riverside, and Imperial. When using the Tehachapi Mountain range as the northern boundary, the following counties could also be included: Santa Barbara, Ventura, San Luis Obispo and Kern.
Southern California is a heavily developed urban environment. It is one of the most urbanized regions in the United States, second only to the Washington, D.C./New York/Boston megalopolis. The dominant areas are Los Angeles, San Diego, and Santa Ana/Orange County; each of which is the center of their respective metropolitan areas, which comprise numerous other cities and communities. Review the metropolitan pages for more information regarding these cities, the economy, demographics, etc.
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.