The Seattle Art Museum is getting a massive infusion of art that will transform it as surely as any building project could. More than 1,000 artworks from 40-plus private collections will enrich the experience of SAM for visitors and scholars, raise the museum's national profile, and increase its ability to bargain for enviable art loans from other museums.

The double occasion for all this gift-giving is the museum's 75th birthday, coming in 2008, and its physical makeover, including the new Olympic Sculpture Park, an improved Seattle Asian Art Museum, and the expansion of the downtown flagship facility, reopening May 5 with double the space for art.

"It really transforms the museum into a major museum," director Mimi Gates said. "We were building the [new facility] to keep the great art in Seattle, in Seattle."

The press office at Christie's confirmed reports that put the estimated value of the donations, if they were to come to auction, at about $1 billion.

Not all of the art will arrive at once; some is promised over a period of time or in a will. Of the 1,000 gifts, about 200 will be on display when the museum opens in May. The gifts cover every area of art: modern and contemporary, American, European, Native American, African and Oceanic, and Asian.

The greatest boost is to the modern and contemporary department, which now will be able to hold its own with a museum like, say, the Dallas Museum of Art, which has respectable holdings both in range and depth, said Michael Darling, the SAM curator who oversees the department. (The DMA also recently received a bequest from a bloc of collectors: 900 works valued at more than $300 million, according to the museum.)

SAM will gain modernist icons: Constantin Brancusi's Bird in Space (1926) and Alberto Giacometti's The Dog (1951), both from Jon and Mary Shirley, and Edward Hopper's Chop Suey (1929), from Barney Ebsworth. The museum will be able to tell full stories about artists it could once only introduce in isolated glimpses. Gerhard Richter is an example. The museum "could easily get up to 10, if not more" Richter paintings, and previous to this, the museum had none, Darling said. Filing in the door will be several paintings each by Mark Rothko, Philip Guston, Sigmar Polke, Anselm Kiefer, and Francis Bacon.

Other artists on the add list include Chuck Close, Alexei Jawlensky, Robert Rauschenberg, Willem de Kooning, Clyfford Still, Jackson Pollock, Donald Judd, Carl Andre, John Chamberlain, Ed Ruscha, Cindy Sherman, Robert Irwin, John Currin, Maurizio Cattelan—the long list, in fact, reads like an art-history textbook index, especially when it comes to postwar art.

The Virginia and Bagley Wright Collection is the most extensive gathering of modern and contemporary art in the Northwest, now on its way to SAM, after the Wrights' long relationship with the museum.

Two of the collections were surprise coups: the Marshall and Helen Hatch Collection of 100 seminal works by the Northwest "mystics," which had earlier been publicized as heading to the Museum of Northwest Art instead; and Barney Ebsworth's nationally coveted stash of early American modernism, previously talked about as bound for the National Gallery of Art, with which Ebsworth has been involved for several years.

Ebsworth's 65 paintings and drawings include a Georgia O'Keeffe abstraction the collector picked up from the artist's own holdings, and one of Marsden Hartley's treasured German soldier paintings—the only one left in private hands, Ebsworth said. There are also works by Alexander Calder, Elie Nadelman, John Marin, William Glackens, Charles Demuth, and Arthur Dove.

Ebsworth lived in St. Louis for all 69 years of his life before moving to Seattle four years ago. His then wife was a Seattleite who urged him to move west, and two months before they did, she left him. Now, the loss is St. Louis's.

"For me, giving to your local museum is the right thing to do, unless your local museum doesn't show any sign of doing real things," Ebsworth said. "But the energy happening here!"

He means the park, the successful capital campaign (SAM has raised $177 million of $180 million toward building costs), and curators such as American art specialist Patti Junker, Darling, and others.

Plus, architecture regularly inspires collectors who want their works to be seen in high-profile environments. (Ebsworth in particular is an architecture fan; he saved a Frank Lloyd Wright house in St. Louis and is attempting to commission a church by Tadao Ando for the Seattle area. It would be Seattle's first Ando.)

Ebsworth likes the new facility's architecture. Designed by Portland's Allied Works, its spaces are regular and modernist compared to sculptural museums. Because of the restrictions that come from abutting the Washington Mutual bank tower by NBBJ, Allied Works "had to build a normal building," Ebsworth said.

In its capital campaign, the museum has raised $24 million toward "the acquisition of art and other enhancements." But no museum could raise enough money to buy the equivalent of these amassed gifts from Ebsworth, the Shirleys, the Wrights, the Hatches, Susan and Jeffrey Brotman, Jane Lang Davis, Ann and Tom Barwick, Richard and Elizabeth Hedreen, Vi Hilbert, and others.

Together, the donors represent the best in collecting in Seattle—except big-timers Paul Allen and Bill and Melinda Gates. SAM director Gates, Bill's stepmother, was mum on whether more announcements will be forthcoming.

"When we have more announcements to make, we'll make them," Gates said.

jgraves@thestranger.com