In 1900, an epidemic of bubonic plague began after a ship brought with it rats infected with the disease. The area most affected was San Francisco’s Chinatown. Though the epidemic was recognized by medical authorities in March 1900, its existence was denied for more than two years by California’s Governor Henry Gage. This denial was made to protect the reputations of San Francisco and California and to prevent the loss of revenue due to quarantine. In 1902, Gage lost re-election and the new Governor George Pardee implemented medical solutions and the epidemic was stopped in 1904. During this two year period, there were 121 cases identified, 119 of whom lost their lives.
In the early morning hours of April 18, 1906, a major earthquake struck San Francisco and northern California. As numerous buildings collapsed, gas lines were ruptured which started a great fire across the city which burned out of control for several days. Though the Presidio Artillery Corps attempted to contain the blaze by dynamiting blocks of buildings to create firebreaks, more than 75% of the city was in ruins before the fire was contained. In the wake of this disaster, as many as 3,000 people died, more than 200,000 were injured, more than half of the city’s population of 400,000 were left homeless, and the estimated damage was about $400 million. The death toll from this event is the highest from a natural disaster in California history.
The process of rebuilding began immediately but it would take several years. In the meantime, trade, industry, and people were diverted south to Los Angeles. While the city was still rebuilding, a second epidemic of bubonic plague hit in the summer of 1908. This time, 160 cases were identified in all areas of the city, but due to the quick actions of the authorities, the mortality rate was lower this time, with 78 people dying of the disease.
In 1915, the Panama–Pacific International Exposition, a world’s fair, was held in San Francisco from February 20 to December 4, 1915. Though the purpose of the exposition was to celebrate the completion of the Panama Canal, it was widely seen as San Francisco’s opportunity to showcase its recovery from the 1906 earthquake. The fair was built on 636-acre site along the northern shore, between the Presidio and Fort Mason.
During the Great Depression, not a single San Francisco-based bank failed and in fact, the city took on several large engineering projects including the construction of the Francisco-Oakland Bay Bridge and the Golden Gate Bridge, which were completed in 1936 and 1937, respectively. It was also during this period that Alcatraz, a former military stockade, began its service as a federal maximum security prison.
San Francisco held another world’s fair in 1939 and 1940. The Golden Gate Exposition celebrated the city’s two newly built bridges. To accommodate the fair, Treasure Island was built near where the Oakland span and the San Francisco span of the Bay Bridge join. Dredging for the flat, geometrically-shaped, artificial island, began in February 1936 and 19 million cubic yards of fill were required for the 385-acre site. Afterward, the island was taken over by the US Navy from 1941 to 1997.
During World War II, San Francisco’s military defense properties were hubs of activity. Fort Mason became the primary port of embarkation for service members shipping out to the Pacific Theater. This created numerous jobs in the area bringing in yet more people.
After the war, returning servicemen and significant immigration increased the city’s population again. In the next decades, San Francisco became a magnet for America’s counterculture with the rise of “hippies,” the Sexual Revolution, the Peace Movement growing from opposition to United States involvement in the Vietnam War, and the Gay Rights Movement. These activities cemented San Francisco as a center of liberal activism in the United States.
Later, came the boom of the dot-com industry in the late 1990s as startup companies, entrepreneurs, and computer experts moved into the city.
Today, San Francisco is the 13th-most populous city in the United States, and the fourth-most populous in California, with nearly 900,000 residents. The high demand for housing, driven by its proximity to Silicon Valley, and the low supply of available housing has led to the city being one of America’s most expensive places to live.