The flag of San Diego, California, is an equal vertical tricolour of red, white, and golden yellow, with a stylized version of the San Diego city seal in the center of the flag, entirely inside the white stripe. Semicircling the lower section of the state seal, in black, is the word "1542".
Red and white are the main colours of the flag of California. The city seal represents the city of San Deigo and its citizens. 1542 is the year that Juan Rodriguez Cabrillo claimed the current San Diego area for Spain, whose colours, red and gold, are represented on the San Diego city flag.