San Diego Bay is a natural harbor and deepwater port located in San Diego County, California near the US-Mexico border. It is 12 miles (19 km) long and 1 to 3 miles (1.6 to 4.8 km) wide. The bay is surrounded by the San Diego metropolitan area, which includes the cities of San Diego, National City, Chula Vista, Imperial Beach and Coronado. Considered to be one of the best natural harbors on the west coast of North America, it was colonized by Spain beginning in 1769. Later it served, and continues to serve to this day, as a home port of major assets, including several aircraft carriers, of the United States Navy's Pacific Fleet.