But Still was as careful in planning his estate as he was in controlling his work. His will dictated that the collection be bequeathed to an American city that would erect a museum dedicated entirely to him—and agree not to sell any of it. For the next 30 years, his paintings were stored in warehouses, while his widow sought a suitable home for them.

Denver won the rights to the museum in 2004 (an earlier attempt in 1999 failed), agreeing to erect a new building next to the Denver Art Museum. In March, the museum unveiled plans for the $33 million facility, designed by the Portland, Oregon/New York firm Allied Works Architecture; construction is expected to begin next year.

The museum has helped boost the market for Still’s works. Before it was announced, Still’s paintings were selling in the $1 million to $4 million range at auction. A 10-by-9-foot painting sold for nearly $8 million last year at Christie’s, and Sobel says it could have gone for more if not for its size—too big for most collections to handle. Prices in private sales are likely to have been much higher.

The Zwirner & Wirth gallery in New York has facilitated three private sales of Still’s work since the 2006 Christie’s auction, says director and partner Kristine Bell. While prices haven’t reached the blockbuster level, they have been trending upwards.

“The prices for a very good one are going to be much, much higher than for the next best,” says Michael Findlay of Acquavella Galleries in New York. Other gallerists said it had been years since they’d had the opportunity to sell one of his paintings and longer since they’d seen a good one. “We haven’t sold one in a long time,” Findlay says.

The Denver Art Museum previewed a selection from Still’s estate last summer, marking the first time many art historians and collectors laid eyes on some of his major works. The show was so popular, drawing 100,000 visitors, that the museum extended it through November.

The upcoming Christie’s sale will be the first since the Denver preview, and though it certainly won’t be the last, the sale will prove whether it whetted collectors’ appetites for more. While the 13 works in the preview, like the rest of the estate, will never be up for sale, the attention the museum will bring to Still’s work might mean that the timing is right to invest in a piece like 1946.

“Every single time his work comes up,” Manley says, “it’s a test of his market.”