After the war, hundreds of land developers bought land cheap, subdivided it, built on it, and got rich. Real estate development replaced oil and agriculture as southern California's principal industry. In 1955, Disneyland opened in Anaheim. In 1958, Major League Baseball's Dodgers and Giants left New York City and came to Los Angeles and San Francisco, respectively. The population of California expanded dramatically, to nearly 20 million by 1970.

California's growth after World War II was fueled in part by an arms race with the Soviets and the growing defense industry. In 1962, about 40 percent of the nation's 6-billion dollar military research contracts went into California for testing technology such as planes and bombs.