At the end of World War II, more than seven million soldiers returned from Europe and Asia. Throughout the country there weren't enough houses for them. Many of those who had been stationed in California wanted to relocate there. About one million soldiers moved to Los Angeles between 1945 and 1950, and an additional two million in the 1950s. Los Angeles developers took over the orange groves and turned them into residential tracts.

World War II had just ended when, in October 1945, Life magazine ran a 13-page essay by photographer Nina Leen titled “The California Way of Life,” which depicted the lifestyle of (White) middle-class Californians as one of leisure and consumption, centered around the single-family home with a yard, a pool and a garage, and therefore credited southern California with "elements of Utopia".

The Los Angeles economy also benefited in the 1950s by the emergence of the television studios, as the television set replaced the radio as the top entertainment and news device in millions of homes. In 1946 there were only six thousand television sets in the USA, and all of them in New York's metropolican area. By 1949 there were three million in many more cities, and that number more than doubled in 1950, and then it decupled in the following decade reaching to 52 million in 1960. Television became the dominant broadcast medium during the 1950s.

Los Angeles, the movie capital of the world, quickly pivoted towards television programming. The three networks that would come to dominate television broadcasting were born as radio networks: the National Broadcasting Company (NBC), spun off in 1926 from the Radio Corporation of America (RCA); the Columbia Broadcasting System (CBS), founded in 1927; and the American Broadcasting Company (ABC), spun off in 1943 from NBC when the government mandated a divestiture of NBC's quasi-monopoly. All three established their West Coast headquarters in Los Angeles: NBC in 1938 on Sunset Boulevard in Hollywood (known as Radio City West), ABC in 1948 east of Hollywood, and CBS in 1949 on Sunset Boulevard in Hollywood.

Television broadcasting was authorized by the US government in July 1941. Both NBC and CBS debuted their television programming on the same day in New York (WNBT was the NBC television station and WCBW the CBS one), and ABC followed in 1948. Their first hit series were mostly produced in New York, like CBS' "The Ed Sullivan Show" (1948-71) and NBC's variety show "Your Show of Shows" (1950–54). ABC's "American Bandstand" (1952-89) was hosted since 1956 by Dick Clark in Philaldelphia. But soon the center of mass shifted towards Los Angeles: NBC's "Dragnet" (1951-59) and Johnny Carson's "The Tonight Show" (1962–92) were made in Burbank; NBC's "Star Trek" (1966–69) in Culver City and Hollywood; CBS' sitcom "I Love Lucy" (1951-57) was made in Hollywood; and ABC's many hits, like the sitcom "The Adventures of Ozzie and Harriet" (1952–66), that promoted the stereotype of the idealized middle-class family, "The Andy Griffith Show" (1960–68) and "The Brady Bunch" (1969–74), all of them in Hollywood. In 1950 Music Corporation of America or MCA, the largest talent agency in the world, rented studios in Hollywood to produce "The Adventures of Kit Carson" (1951–55). And there were many others.

Television added to a wild mix of wealth-generating businesses. During the Great Depression, Los Angeles' oil magnate Jean Paul Getty expanded his business in the USA, and after the end of World War II he expanded it in the Middle East, becoming by 1957 the richest man in the country. An avid art collector, in 1954 he turned his Malibu mansion into a private museum (which after his death would become the largest and richest art institution in the world), and in 1974 he opened to the public a replica of a Roman villa stuffed with Roman antiquities (an imitation of the Villa of the Papyri at Herculaneum in Italy). At the time he had moved to a sprawling 16th-century estate in England, surrounded by a harem of pretty girls, with a pet lion, and made the international headlines mostly not for his art but for the kidnapping of his teenage grandson John Paul Getty III in Italy in 1973.

Another oil tycoon and an art collector was Armand Hammer, who became rich by doing business with the communists of the Soviet Union in the 1920s (he was the son of a Russian Jew who co-founded the Communist Party of the USA) and by selling alcohol legally (for medicinal purposes) during the Prohibition era through his United Distillers of America, finally purchasing the struggling Occidental Petroleum in 1957 and expanding its oil business all over the world.

Hollywood, while declining due to the competition of television, had created manywealthy and powerful people who ran the film studios: Jack Warner, Louis Meyer, Samuel Goldwyn, Karl Laemmle, Walt Disney, Darryl Zanuck, Adolph Zukor, ... And then there were the movie stars (countless), and the filmmakers (from all over the world). And the singers, popularized by both radio and cinema: Bing Crosby, Frank Sinatra, Dean Martin, Elvis Presley, Nat King Cole, ...

The county of Los Angeles expanded rapidly after World War II, with its total population increasing by more than one million between 1940 and 1950 (2.78 million to 4.15 million). Los Angeles' real-estate developers ranked among the most daring and ambitious in the nation.

In 1947 an open-air shopping mall opened just southwest of Los Angeles (now a Black neighborhood) built by developer Paul Trousdale on land once owned by Elias Baldwin where few people lived (part the old Rancho La Cienega): it was clearly meant to serve the car-equipped middle class. The Broadway Crenshaw Center (later renamed Baldwin Hills Crenshaw Plaza) featured two buildings in the Streamline Moderne style: a The Broadway store, designed by Albert Gardner, and run by Edward Carter (the store that made the mall famous), and a store of the St Louis-based May Company, designed by Albert Martin's firm.

Bob Symonds, who had worked with A.W. Ross on the "Miracle Mile" project, created in 1951 the open-air Valley Plaza shopping center in the San Fernando Valley. The genius of the suburban shopping mall was Victor Gruen, an Austrian who had designed in Minnesota the first enclosed shopping mall in the country, Southdale Mall (1956), and who designed several in California, starting with the Westfield Valley Fair in San Jose (1956), and quite a few in the Los Angeles area (such as the South Bay Center in Redondo Beach in 1959), besides planning the town of Valencia in 1965 (more famous for the rollercoaster-crazy amusement park Magic Mountain that opened in 1971). In 1953 developer Ben Weingart, inspired by the success of William Levitt's Levittown (built in Long Island in 1947), inaugurated a 17,000-home community near Long Beach named Lakewood, the largest planned city in the country yet, which heralded a new era of mass-produced housing. It generated a home-buying frenzy among war veterans (who, by law, were able to get home loans at very favorable conditions). Weingart's partner in that venture was Mark Taper (a Polish Jew who had already made a fortune in England), who specialized in low and middle-income suburban housing for returning soldiers. William Zeckendorf (a French Jew who was already a famous New York developer) turned the studios of 20th Century-Fox into Century City (construction began in 1960). Henry Kaiser and home builder Fritz Burns formed Kaiser Community Homes which built the 3,000-home Panorama City in the San Fernando Valley between 1947 and 1952, a short distance from a General Motors factory. Kaiser applied the same idea to cities of the Bay Area where car manufacturers had opened factories, as in San Leandro (Chrysler) in the East Bay.

John Entenza took over the magazine Arts & Architecture in 1940 and became a strong promoter of modernist architecture. The years after World War II marked the apotheosis of modernist architecture in Los Angeles, with homes such as the "Eames House" (1949) by Charles Eames in Pacific Palisades and the "Henry Salzman House", aka "Case Study #16" (1953), by Craig Ellwood. Entenza's own house in Pacific Palisades (1949) was designed by Charles Eames and Eero Saarinen. These modernists also toyed with steel frames, notably the Greek-born Raphael Soriano (Richard Neutra's assistant) with the house for architectural photographer Julius Shulman (1950) and Pierre Koenig with his "Bailey House", aka "Case Study #21" (1959), both in the Hollywood Hills.

Julius Shulman, who opened his photography studio in Los Angeles in 1950, documented four decades of Los Angeles architecture.

The specialist of "tracts" of single-family houses was in the Bay Area: Joe Eichler (the son of an Austrian Jew), who democratized the "modernist" style of famous architects like Frank Lloyd Wright and Ludwig Mies van der Rohe. He built more than 3,000 homes in Santa Clara County, starting with Sunnymount Gardens in Sunnyvale (1949) and University Gardens in Palo Alto (1950). His style was the brainchild of young architects Robert Anshen and Claude Oakland, and later of Quincy Jones, who designed the Greenmeadow Tract in Palo Alto (1955).

In 1960 the Oklahoma developer Jack Foster purchased an island of the Bay, Brewer's Island, which was owned by the wealthy Shilling family, the heirs of an August Schilling who had made a fortune in spices, coffee and tea. Foster undertook a vast reclamation project, filling the island’s marshes with 14 million cubic meters of sand transported from the nearby San Bruno Shoal on some of the largest barges in the world. Within four years, he and his sons had laid out lagoons, parks, and winding streets, transforming the island into a new city, a modern paradise by the bay, now known as Foster City. Between 1963 and 1968, more than 200 homes were constructed by Joe Eichler, working with architects such as Claude Oakland and John Brooks Boyd.

The Telesis exhibition of 1940 had prompted San Francisco to start planning its development. Their 1950 exhibition "The Next Million People" spurred the nine counties and 69 cities of the Bay Area to coordinate their urban plans. Meanwhile, Frederick Law Olmsted's spiritual heirs were the landscape architects Thomas Church, who shaped the Donnell Ranch Garden (1948) in Sonoma, Garrett Eckbo, who designed the estate for art patrons Sidney and Frances Brody in Holmby Hills (1949) in collaboration with architect Quincy Jones and published the influential book "Landscape for Living" (1950), Lawrence Halprin, who designed the planned community of Sea Ranch (1964) north of San Francisco, and Robert Royston, who specialized in suburban parks. All of these landscape architects were trained and/or taught at UC Berkeley.

In 1959 the University of California acquired James Irvine's ranch (60 km) southeast of Los Angeles) and charged architect William Pereira to build an entire city around a new campus (UC Irvine), which opened in 1965 (the city itself was finally incorporated in 1971).

During the 1960s San Diego became a major hub of scientific research. UC San Diego was established in 1960, actually in nearby La Jolla, thanks to the efforts of oceanographer Roger Revelle (one of the first scientists to speak of global warming). La Jolla already hosted the Scripps Research Institute for research on diseases. In 1963 Jonas Salk, inventor in 1955 of the first commercial polio vaccine, opened the Salk Institute for Biological Studies in La Jolla, housed in a futuristic building designed by Philadelphia architect Louis Kahn. The location so far away from the established centers of Biology (possibly recommended by Robert Oppenheimer) actually helped attract talents such as Francis Crick, one of the discoverers of the double-helix structure of DNA in 1953, Jacques Monod, who in 1961 Jacques Monod had co-discovered gene regulation, and Robert Holley, who in 1965 had discovered transfer RNA. UC San Diego also created an important school of Cognitive Psychology, hiring Peter Lindsay from the University of Toronto in 1966, Don Norman from Harvard in 1966 and David Rumelhart from Stanford in 1967 (the trio came to be known as "the LNR research group"), and later in 1978 Geoffrey Hinton, the future guru of Artificial Intelligence.

Among the gurus of modernism, Lloyd Wright built the Wayfarers Chapel in Rancho Palos Verdes (1951) and Louis Kahn the Salk Institute in San Diego (1965). The other architectural wonders of the era were designed by local architects. Wayne McAllister's Bob's Big Boy restaurant in Burbank (1949) and John Lautner's Googies Coffee Shop in Hollywood (1949) launched the "Googie" style of architecture. Archibald Quincy Jones designed the modernist house for art collector Sidney and Frances Brody in Holmby Hills (1949). John Elgin Woolf and Paul Revere Williams (the rare Black architect of the time) designed houses for countless movie stars in what came to be known as the "Hollywood Regency" style. Williams designed the residence of the Lebanese Christian physician Assad Abdun-Nur and his wife Amenie (1947) in Tarzana (San Fernando Valley), the Tevis and Colleen Morrow house in Pacific Palisades (1949), in collaboration with landscape architect Thomas Church, and the modernist house for Lucille Ball and Desi Arnaz in Palm Springs (1954). Wallace Neff designed luxury homes like the one for Fred Niblo in Beverly Hills (1926), the one for Sol Wurtzel in Bel Air (1931), the one for Groucho Marx in Beverly Hills (1956) and the one for Ralph Chandler in Hancock Park (1960). Welton Becket's Capitol Records Building in Hollywood (1956), the first circular office building, and John Lautner's Chemosphere in Los Angeles (1960) were other important buildings of the era. John Lautner also designed the Sheats–Goldstein house in Beverly Hills, originally (1963) built for Paul and Helen Sheats but later renovated until Lautner's death (1994) by new owner James Goldstein, and Bob Hope's "Space Home" in Palm Springs (1979). Edward Fickett designed the modernist house for George and Miriam Jacobson (1965) near Neutra's Lovell House. William Pereira designed the Geisel Library at UC San Diego (1960), the Theme Building at Los Angeles International Airport (1961) in collaboration with Paul Revere Williams, and the skyscraper of Crocker Citizen's Bank (1969), which was the new tallest building in Los Angeles. William Krisel designed the first modernist neighborhood in the desert: Twin Palms Estate, homes with a characteristic butterfly-shaped roof, located in Palm Springs (1956-59). The Pasadena-based firm of Thornton Ladd and John Kelsey (University of Southern California classmates) designed the Marco Wolff House (1958) in Los Angeles, the John Kelsey House (1961) in Pasadena, the Pasadena Art Museum (1969) and the California Institute of the Arts (1970).

In 1953 three major freeways (the Pasadena, Hollywood and Santa Ana) were connected in downtown Los Angeles by a four-level interchange that was a world's first. Nicknamed the "stack", it became an iconic image of Los Angeles just like the Tour Eiffel in Paris. Paris had a panoramic tower for people, Los Angeles had a freeway interchange for cars.

The Los Angeles County Museum of Art (LACMA) was established in 1961, largely through the efforts of businessman and art collector Edward Carter, and in 1965 moved to a new complex designed by William Pereira in the "Miracle Mile" section of Wilshire Boulevard: three buildings named after the three main donors (financier Howard Ahmanson, theater actress Anna Bing, who was the wife of real-estate developer Leo Bing, and oil magnate Armand Hammer). The first director was William Fargo's grandson Richard Brown who hired as curator Maurice Tuchman from the Guggenheim Museum in New York.

At the same time, Dorothy Chandler, the wife of Los Angeles Times publisher Norman Chandler (Harry's son) who had become the main philanthropist of the Los Angeles Philharmonic Orchestra after the death of the orchestra's founder William Andrews Clark in 1934, led the effort to build a performing arts center in Bunker Hill. The Memorial Pavilion opened in December 1964 with a young Zubin Mehta as the new conductor of the Philharmonic. More buildings were added, the Ahmanson Theatre (1967) and the Mark Taper Forum (1967), both designed by Welton Becket's firm, and the whole became known as the Music Center.

In 1960 Los Angeles' population (2.5 million) surpassed Philadelphia as third in the nation.

In 1940 California's population was almost seven million, having doubled in 20 years, and then it passed ten million by 1950 and jumped to 15.7 million by 1960. In 1962 California passed New York to become the most populous state, and in 1971 it reached 20 million.