A lone painting by a celebrated contemporary artist turned into a windfall on Wednesday night for a small municipal agency in Chicago.
The painting, Kerry James Marshall’s “Past Times,” sold for $21.1 million at Sotheby’s in New York, nearly 900 times the $25,000 that the Metropolitan Pier and Exposition Authority spent on it in 1997, and a record for the artist. In a statement, Lori Healey, the authority’s chief executive, said the M.P.E.A. was “thrilled” by the auction results, adding that the price tag ended up “far exceeding anyone’s expectations.”
The authority, which was formed by the state of Illinois, oversees McCormick Square, which includes the McCormick Place Convention Center, the Wintrust Arena and two hotels along the lakefront. It is required to spend a portion of its budget on art displayed to the public. As a result, it currently possesses more than 100 pieces from a wide variety of artists.
After it was acquired for McCormick Square, the painting hung in the hallway of the convention center for years with very little protection, making it liable to theft or damage, even as its value grew. The authority lent the piece out for the traveling show, which began at the Museum of Contemporary Art Chicago and also traveled to the Museum of Contemporary Art Los Angeles.
Officials began to question whether it was appropriate to keep the painting at McCormick Place. They sent it to storage while they contemplated what to do with it.
“We’re not a museum,” said Ms. Healey said in an interview before the auction. “We’re a convention center. We’re not set up to display a piece of art of this value.” 
Earlier this year, the agency decided to put it up for public auction. Sotheby’s had estimated it would sell for $8 million to $12 million. It ended up selling for almost double the top-end estimate. Ms. Healey said the money would be put toward the infrastructure needs of the campus.
