San Diego, the oldest city in California, was first inhabited by the Kumeyaay people for thousands of years before European contact.

Juan Rodríguez Cabrillo, sailing under the Spanish flag, landed in San Diego Bay in 1542, marking the first European expedition to present-day California.

Mission San Diego de Alcalá, established in 1769 by Father Junípero Serra, was the first of 21 Franciscan missions in Alta California, playing a crucial role in the region's colonization.

San Diego's strategic location on the Pacific Ocean and proximity to the Mexican border has heavily influenced its development, fostering a unique blend of cultures and economies.

The city boasts a diverse geography, encompassing beaches, canyons, mountains, and a desert climate, contributing to its appeal as a tourist destination and a haven for outdoor activities.

San Diego's population has experienced significant growth, transforming from a small Spanish settlement to the eighth-largest city in the United States, with a diverse ethnic makeup.

The U.S. Navy has a major presence in San Diego, with several naval bases, making it a significant center for military activity and contributing substantially to the local economy.

Biotechnology, tourism, defense, and international trade are key pillars of San Diego's economy, driving innovation and attracting a skilled workforce.

Balboa Park, a 1,200-acre urban cultural park, houses numerous museums, gardens, and the San Diego Zoo, attracting millions of visitors annually and enriching the city's cultural landscape.

Old Town San Diego State Historic Park preserves the city's early history, showcasing meticulously restored buildings and offering a glimpse into life during the Mexican and early American periods.

Comic-Con International, held annually in San Diego, is one of the largest comic book and pop culture conventions in the world, drawing hundreds of thousands of attendees and boosting the local economy.

The Cabrillo National Monument commemorates Juan Rodríguez Cabrillo's landing and offers panoramic views of the Pacific Ocean, downtown San Diego, and Coronado Island.

San Diego's commitment to scientific research and development has fostered a thriving biotechnology industry, with numerous research institutions and companies contributing to advancements in medicine and technology.

The influence of Mexican culture is evident in San Diego's cuisine, architecture, and traditions, particularly in neighborhoods like Barrio Logan, known for its Chicano Park and vibrant murals.

While not a UNESCO World Heritage Site in its entirety, the Mission San Diego de Alcalá is a contributing property to the California Mission System, which is considered for future nomination.