Whenever Eli Broad went shopping, he’d do some selling. A multibillionaire who made his fortune in homebuilding and retirement funds, Broad would pick up a Koons or Kusama -- and make a pitch for Los Angeles.

At 82, Broad is a modern-day Medici, having devoted hundreds of millions to his singular, seemingly quixotic quest: to transform a sprawl of traffic and tabloid celebrity into a vital center for contemporary art rivaling New York or London. The culmination is a 120,000-square-foot museum bearing the Broad name, which opens Sunday in downtown Los Angeles. The story behind it is about vision, money and power. And, as far as Broad’s concerned, success.

“We’re really the contemporary-art capital of the world,” he says from his 30th-floor office in L.A.’s Century City district. “New York still is the commercial-art capital of the world -- but a month doesn’t go by when one of their galleries doesn’t move to Los Angeles.”

Top international galleries are opening local outposts, with Sprueth Magers, which has spaces in Berlin and London, bypassing Manhattan to have its first U.S. location on the other coast. Artists can be noticed and sell without having to leave town. That’s something relatively new for L.A., where the noise made by the dominant creative industry of movies and television tends to drown everything else out.

Maybe it would have happened anyway; the city, after all, is home to such icons of postwar art as Ed Ruscha and John Baldessari, top-ranked art schools and galleries including Regen Projects and Blum & Poe. It’s where Larry Gasogian started his art-dealing empire. But Broad’s getting a good deal of the credit, showered with it this week before the opening of the $140 million museum he built to showcase works in the $2 billion collection he and his wife Edythe amassed over five decades.

Simon de Pury, former chairman and chief auctioneer at Phillips de Pury auction house, calls Broad a “cultural animator” who “single-handedly made Los Angeles the main creative place at the moment.” Lisa Dennison, chairman of Sotheby’s North and South America and a former director of the Solomon R. Guggenheim Museum, says Broad’s been like a star quarterback for the city, recalling how he’d host exclusive receptions at international fairs and biennales to champion his favorite cause. “He’s taken L.A. as a local situation,” she says, “and made it global.”

Broad’s an example of the clout one hard-driving patron can have in a metropolis that has more than 100 zip codes and is rich with multimillionaires. His net worth is $7.4 billion, according to the Bloomberg Billionaires Index, and he hasn’t been hesitant to tap it. Contributions to local arts and cultural organizations have totaled $915 million, according to the Eli and Edythe Broad Foundation. Gifts haven’t come without strings, or bruised egos, as Broad has sometimes clashed with directors and trustees of the institutions he backs. But he’s widely hailed in L.A. as the city’s most important benefactor.

Donations over the years have included $60 million to the Los Angeles County Museum of Art, where a contemporary-art wing bears the Broad name, despite still-simmering tensions caused by his decision to loan and not bestow artwork to the institution; $23 million to fund what became the Broad Art Center at UCLA; and $30 million to the Museum of Contemporary Art, which he co- founded. That money bailed MOCA out when it was nearly insolvent in 2008, though it continued to struggle. Broad’s controlling role on the board resulted in the arrival in 2010 of New York art dealer Jeffrey Deitch as director and the departure of four artist-trustees, including Ruscha and Baldessari, who said they were unhappy with the direction. Deitch resigned three years into his five-year contract; Baldessari and two others, though not Ruscha, have since returned to the board.

Broad and his wife have also supported schools and medical and scientific research with large donations, and he has sought to buy the Los Angeles Times. He was a leader of the fundraising campaign in the 1990s for the city’s famed Walt Disney Concert Hall, designed by architect Frank Gehry -- with whom Broad had well-publicized disputes during construction -- that is across the street from the Broad museum.

The collection Eli and Edythe Broad put together might alone have catapulted the city into a new center for contemporary art. The couple, individually and through their foundation, have made purchases at galleries, auctions, fairs and directly from artists. In 2006, Broad dropped $11.8 million on Andy Warhol’s small painting of Campbell’s pepper pot soup at a Christie’s auction. In 2005, he paid $23.8 million for David Smith’s stainless-steel “Cubi XXVIII,” the highest price for a piece of contemporary art at auction at the time.