"Washington Crossing the Delaware" has crossed the Mississippi River — bound from Winona's Minnesota Marine Art Museum to Christie's auction house in New York.

The famous painting, which had been on long-term loan to the museum, will be auctioned off May 12 at an estimated price of $15 million to $20 million. Its sale could break a record as the most expensive piece from its time period.

"This is the most significant pre-20th-century American painting to come on the auction market," said Paige Kestenman, a specialist in American painting at Christie's. "It achieved a record for an American painting when it was sold in 1973 at Christie's."

Portraying George Washington in the bow of a small boat as he led a daring attack during the Revolutionary War, the work is the smaller of two surviving versions by history painter Emanuel Leutze (1816-68), who was born in Germany and immigrated to the United States as a child. The second is on display at New York's Metropolitan Museum of Art. A third version was destroyed in an air raid during World War II.

More than 3 feet tall and nearly 6 feet wide, this version of the work hung in the White House from 1979 until 2014, when a Winona couple, Mary Burrichter and Bob Kierlin — founder of the hardware supply company Fastenal — bought it from a private collector. They had help from the late John Driscoll, who was a Minnesota-born, New York-based art dealer.

"Its recognizability gives it staying power but also a certain pop culture kitsch appeal about patriotism," said Jennifer Marshall, associate professor at the University of Minnesota, who specializes in U.S. art and culture from the colonial period to the 1960s.

"It depicts the 1770s but was [finished in 1851] and is sometimes popular, kind of like a Marvel movie-type thing — it is displayed with all these curtains and lights."

The version at the Met was, at various points, rolled up and stored in the basement because it was seen as too patriotic or kitschy. But eventually it came back in vogue.

After buying the painting, Burrichter and Kierlin put it on display at the Marine Art Museum, where they serve as longtime collecting partners. All told, the museum has on display 50 to 60 works owned by the couple, including pieces by Giorgio de Chirico, Max Pechstein, Edward Hopper and Toulouse-Lautrec.

A hidden gem about two hours south of the Twin Cities, the museum's collection includes other striking examples of 19th-century American paintings from the Hudson River School, important Impressionist works and 20th-century European pictures.

The couple terminated the loan of the Washington painting this year, and it was taken down in March. Though the painting seemed like the crown jewel of the museum, it was never part of the permanent collection nor was there a fixed end date for the long-term loan.

"The museum is clearly happy to have had it here for as long as it did," museum director Scott Pollock said. "There's been a lot of effort put into its interpretation, telling its story, creating programs around it."

Saying goodbye is never easy, though.

"It's hard because people are attached to it," Pollock said.

"It's a moment to reflect on how this particular piece, the museum and its identity was wrapped around it," he said. "It was on the front page of our website for a number of years, and there are many interpretations of that historical moment that we would love to uncover and unpack.

"I think that's part of the work ahead."

Correction: Previous versions of this story misstated when the smaller version of “Washington Crossing the Delaware” was painted.