San Diego is the eighth-largest city in the United States and second-largest city in California and is proudly referred to by locals as "America's Finest City". The city is located on the coast of the Pacific Ocean in Southern California, immediately adjacent to the Mexican border. The birthplace of California, San Diego is known for its mild year-round climate, its natural deep-water harbor, and its long association with the U.S. Navy. The population was 1,301,617 at the 2010 census.

Historically home to the Kumeyaay people, San Diego was the first site visited by Europeans on what is now the West Coast of the United States. Upon landing in San Diego Bay in 1542, Juan Cabrillo claimed the entire area for Spain, forming the basis for the settlement of Alta California 200 years later. The Presidio and Mission of San Diego, founded in 1769, were the first European settlement in what is now California. In 1821, San Diego became part of newly independent Mexico, and in 1850, became part of the United States following the Mexican-American War and the admission of California to the union.

The city of San Diego recognizes 52 individual areas as Community Planning Areas. Within a given planning area there may be several distinct neighborhoods. Altogether the city contains more than 100 identified neighborhoods.

Downtown San Diego is located on San Diego Bay. Balboa Park encompasses several mesas and canyons to the northeast, surrounded by older, dense urban communities including Hillcrest and North Park. To the east and southeast lie City Heights, the College Area, and Southeast San Diego. To the north lies Mission Valley and Interstate 8. The communities north of the valley and freeway, and south of Marine Corps Air Station Miramar, include Clairemont, Kearny Mesa, Tierrasanta, and Navajo. Stretching north from Miramar are the northern suburbs of Mira Mesa, Scripps Ranch, Rancho Peñasquitos, and Rancho Bernardo. The far northeast portion of the city encompasses Lake Hodges and the San Pasqual Valley, which holds an agricultural preserve. Carmel Valley and Del Mar Heights occupy the northwest corner of the city. To their south are Torrey Pines State Reserve and the business center of the Golden Triangle. Further south are the beach and coastal communities of La Jolla, Pacific Beach, and Ocean Beach. Point Loma occupies the peninsula across San Diego Bay from downtown. The communities of South San Diego, such as San Ysidro and Otay Mesa, are located next to the Mexico – United States border, and are physically separated from the rest of the city by the cities of National City and Chula Vista. A narrow strip of land at the bottom of San Diego Bay connects these southern neighborhoods with the rest of the city.

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