San Diego County is a county located near the Pacific Ocean in the far southwest of the U.S. state of California. It is the southwesternmost county in the contiguous 48 states. The population in 2000 was 2,813,834, but a July 2008 estimate placed the population at 3,001,072 people, making it the third most populous county in California, behind its northwestern neighbour Orange County. The county seat is the city of San Diego.
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.