San Diego is a city and the seat of San Diego County in the southwest corner of California, in the United States of America.

It is the second largest city in California (after Los Angeles) and the seventh largest in the United States.

Known for its superb climate and recreational attractions, San Diego also has one of the largest concentrations of military personnel in the nation.

The city is located on San Diego Bay, one of the finest natural harbors in the world. Along its shores is the principal West Coast base of operations for the United States Navy and a busy commercial port.

The city takes its name from the nearby bay, named by Spanish explorer Sebastián Vizcaíno in 1602 in honor of a 15th-century Franciscan, San Diego de Alcalá (Saint Didacus).

In 1769, a presidio (military fort) and mission were established, the first Spanish settlement in what was to become California.