The most southwestern city in the entire U.S. mainland, Imperial Beach is a residential seaside community of around 28,000 people with one of the youngest median ages in Southern California. Average household income is just under $58,000. There are more than six miles of beaches, including a dog beach and some of the best surfing in the county according to locals. Imperial Beach hosts the annual U.S. Open Sand Castle Competition, which brings in over 300,000 visitors, as well as an annual dog surfing competition and international film festival. The South Bay Drive-in, the only drive-in theater in the U.S. with an ocean view, and the Tijuana Estuary are also unique local spots.