Until about 1990, aficionados could still count on a steady stream of pictures coming out of attics and off the walls of early collectors who, seeing prices rise so steeply, were happy to sell Grammy’s landscapes at a tidy profit. But during the past two decades, the attics have been cleared out, and market circulation has come to a screeching halt. “Today major works are no longer in the hands of doctors and lawyers and other ‘little people’ who, at some point, will want to trade up or cash out,” says Godel. “There has been a movement to ‘strong hands’: billionaires who will never need to sell their collections.”

Some of these have already given their holdings to institutions. Notably, the shoe magnate Peter Lunder entrusted his collection of more than 400 works—among them, canvases by Chase, Homer, George Innes and Georgia O’Keeffe—to the Colby College Art Museum, in Waterville, Maine, last May; and the Virginia energy baron James McGlothlin has promised $70 million worth of art, including examples by Homer and Whistler, to Richmond’s Virginia Museum of Fine Arts in 2005. Other megacollectors have founded museums of their own. Five years ago, the Alabama paper czar Jack Warner opened the Westervelt Warner Museum of American Art, in Tuscaloosa, and the Wal-Mart heiress Alice Walton is busy buying works to fill her soon-to-be-completed Crystal Bridges museum, in Bentonville, Arkansas.

Ultrawealthy collectors like Bill Gates and the Denver media mogul Philip Anschutz aren’t selling either. Not only are they immune to the prospect of potential profits, but many of them acquire American art as an expression of national identity. “These people are very patriotic,” says Godel, “and to them these works encapsulate the history of America.” So unlike some collectors of contemporary artworks, Godel says, “they are never going to sell them.”

Meanwhile, more connoisseurs are lining up to buy. “The number of people who want to collect American art has increased tremendously in the past few years,” says Sotheby’s Mitchell. Betty Krulik, a New York private dealer, has noticed this as well. “These days when I get something great,” she says, “there will be at least 20 collectors dying to buy it.”

Maybe it’s the 9/11 effect—collectors deciding to buy “made in the U.S.A.” in the wake of the World Trade Center attack—or the result of more scholarship in the field, or of more museum exhibitions, or maybe it simply reflects the increasing concentration of American wealth, but experts have never seen the American-art field so crowded. Neither have frustrated fans. Cheryl Chase, a Connecticut-based 10-year veteran of this market, complains that “there is now so much competition for the best things that it’s becoming impossible to buy anything.” The Smithsonian’s Harvey adds: “We have always cried ‘scarcity,’ but the problem is bigger now. There are simply too many fisherman in this pond and not enough fish.”

Any major catches now command whopping sums. “Scarcity has driven prices to levels we never could have imagined,” says Christie’s Widing. Take Hotel Window, 1955, one of the few trademark noirish Hopper paintings to come to market in the past few decades. Purchased by Steve Martin at Sotheby’s in 1987 for $1.3 million, the work netted the actor an eye-popping $26.8 million when he sold it at the same venue in 2006. When Polo Crowd, 1908, a rare, desirable work by George Bellows owned by the John Hay Whitneys for almost 70 years, hit the block in 1999, Bill Gates had to pay $27.5 million to take it home. Even less illustrious works bring big bucks. When Breaking Home Ties, 1954, a Norman Rockwell illustration for the cover of the Saturday Evening Post sold to director Steven Spielberg for $15.4 million at Sotheby’s in 2006, old-timers were horrified. “The auctions are now filled with Rockwells,” laments dealer Maroney (Sotheby’s last American-art sale, in November 2007, included 13 works by the illustrator). “If people who knew the market in the 1960s came to a sale today, they would say that they are loaded with scraps—priced at over $1 million apiece.”