San Diego has been inhabited by humans for perhaps 20,000 years along the coast, and 12,000 years in the desert. The primary Native American people to settle in San Diego's coastal and inland regions were the Kumeyaay, seasonal hunters and gatherers. These people were characterized as "…fine in stature and carriage, affable and gay," according to Father Junipero Serra, who built the first California mission in the San Diego area in 1769. "They brought fish and mollusks to us, going out in their canoes just to fish for our benefit. They have danced their native dances for our entertainment," he wrote in his journal.
These peaceful people greeted the first European to visit the region in 1542, Portuguese explorer Juan Rodrigues Cabrillo who sailed his ship the San Salvador from Navidad, New Spain. Cabrillo named the area San Miguel and declared it a possession of Spain. An estimated 20,000 to 30,000 Kumeyaay lived in the San Diego area at the time.
After Cabrillo, Spain's Sebastián Vizcaíno arrived in his flagship San Diego in 1602 to map the California coast. Vizcaíno in turn named the area San Diego, not for his ship but for the Catholic saint San Diego de Alcalá.
The present Old Town had its origins in the 1700s when the Spanish ships San Antonio and San Carlos sailed into San Diego Bay in 1769, and the Spaniards established a military post, Presidio of San Diego on Presidio Hill near the present site of Old Town. Immediately afterward, the first of 21 California missions was then founded there on the hill, Mission San Diego de Alcalá.
By 1774, the first colonists arrived in San Diego, and one year later, the Kumeyaay people attacked the mission which had by then relocated a few miles east, and set it on fire. This was the first act revealing a deep mistrust between the native Kumeyaay and the Spanish missionaries, a mistrust that would continue until Mexican independence in 1821. Indeed, the Kumeyaay became the most resistant of all California Indians to subjugation and European intrusion. Even so, by 1797, the mission included the largest native population in Alta California.
In 1821, New Spain – or Mexico – won independence from Spain, and San Diego came under Mexican rule. In 1846, the United States declared war on Mexico, and in 1848 the Treaty of Guadalupe Hidalgo was signed, ending the war and defining the boundary between the U.S. and Mexico – all in the midst of the Gold Rush of 1848. San Diego officially became an American city.
By the 1850s, the non-native population reached 650, and San Diego County was created, one of California's original 27 counties. The population increased quickly, and by 1900, it was over 17,000. That year, the U.S. Navy founded its first establishment, the Navy Coaling Station, which further fueled the town's development. In 1903, the Marine Biological Association of San Diego formed, later becoming the world-famous Scripps Institution of Oceanography, the first of many scientific institutions in the area.
San Diego then hosted two World's Fairs, the Panama-California Exposition in 1915, and the California Pacific International Exposition in 1935. Balboa Park was the home of many Spanish colonial-style buildings built for these fairs, many of which have been restored to their original facades.
The military continued to expand its presence after World War II, but cutbacks after the Cold War prompted San Diego to diversify its economy. Since that time, the biotechnology industry has become an increasing player in the local economy, including the Jonas Salk Institute for Biological Studies, opened in 1963.
Urban renewal is a continuing theme in Downtown San Diego, including the restoration of the Gaslamp Quarter and the construction of a large number of waterfront skyscrapers, hotels, restaurants, and other buildings.