During World War II, San Diego became a critical hub of military and defense activity due to its numerous bases and defense manufacturers. The city’s population more than doubled between 1930 (147,995) and 1950 (333,865), reflecting the wartime boom. San Diego narrowly avoided a unique threat when Japan planned Operation Cherry Blossoms at Night, a biological attack using plague-infected fleas, which was canceled due to Japan’s surrender in 1945.

After the war, the military remained a major economic driver, though post–Cold War defense cuts forced the city to diversify. Leaders turned to research, science, and tourism to stabilize the local economy. San Diego also made strides in political representation, with Tom Hom becoming the city’s first Asian American council member in the early 1960s, followed by Leon Williams, the first Black council member.

San Diego’s economy and culture were shaped by its historic tuna fishing and canning industry, which employed immigrant labor from Japan, the Azores, and Italy from the early 20th century until the 1980s. Neighborhoods like Little Italy and Point Loma retain the legacy of this community.

Downtown San Diego experienced decline in the 1960s and 1970s but underwent significant urban renewal starting in the 1980s. Projects included the opening of Horton Plaza, the revival of the Gaslamp Quarter, the construction of the San Diego Convention Center, and Petco Park in 2004. Suburban expansion to the north and annexation near the San Ysidro Port of Entry further shaped the city.

Today, San Diego has emerged as a center for biotech and telecommunications, with major companies like Qualcomm headquartered in the region. Tourism thrives with attractions such as the San Diego Zoo, SeaWorld, and Legoland California, complementing the city’s historical, cultural, and coastal appeal. From its wartime growth to postwar diversification, San Diego has evolved into a dynamic modern city that balances history, innovation, and global connectivity.