San Diego is a major city in the U.S. state of California on the coast of the Pacific Ocean and immediately adjacent to the Mexican border. With a 2020 population of 1,386,932, San Diego is the eighth most populous city in the United States and second most populous in California (after Los Angeles). The city is the county seat of San Diego County, the fifth most populous county in the United States, with 3,338,330 estimated residents as of 2019. The city is known for its mild year-round climate, natural deep-water harbor, extensive beaches and parks, long association with the United States Navy and Marine Corps, and recent emergence as a healthcare and biotechnology development center. The flag of San Diego consists of three vertical bands; colored from left to right; dark red, white and gold. The central white band carries the city seal, which carries the words: “The City of San Diego · State of California · Semper Vigilans.” The last of those three phrases is the city’s official motto, Latin for “ever vigilant.” Under the seal is the number 1542, the year in which Juan Rodríguez Cabrillo first entered San Diego Bay and claimed the area for the Spanish Empire. The red and gold bands come from the colors of Spain’s flag. The flag was adopted on October 16, 1934 by the City Council, after Albert V. Mayrhofer submitted a sample banner on behalf of the California Historical Association, the Native Sons of the Golden West, Native Daughters of the Golden West, and The San Diegans. 4K Resolution.