The painting is iconic — George Washington leading his men across the swirling icy waters of the Delaware to attack Hessian soldiers, still drunk from their Christmas celebrations — if not quite accurate. Yet “Washington Crossing the Delaware” firmly cemented the legacy of the general as the primary hero of the American Revolution.   Now the painting, which hung in the White House for the better part of four decades, will be on sale next month and is expected to fetch as much as a staggering $20 million, according to Christie’s auction house .  One of three versions of the artwork by German American artist Emanuel Leutze, the roughly 3 ½-foot-by-5-foot version for sale, which he completed in 1851 in Dusseldorf, Germany, “was always privately owned and was created so that it could be more easily reproduced by an engraver, who could then mass produce prints of the piece,” the New York Times reported. The better-known 12-foot-by-21-foot canvas version, Leutze’s second, continues to hang at the Metropolitan Museum of Art in New York City, while the first iteration, which hung in the Kunsthalle Bremen in Germany, was destroyed when the museum was bombed during an air raid in World War II.  In 1973, Leutze’s smallest painting of the event sold for $260,000, which at the time was the most anyone had ever paid  for an American painting, Paige Kestenman , a specialist in Christie’s American art department, told the Times.  Sold for $370,000 six years later, the painting was frequently loaned to the White House and was on display during various administrations. The scene, meant to emphasize revolutionary valor and the multicultural nature of the new nation, found a unique home in the nation’s capital.  “Leutze’s ‘Washington Crossing the Delaware’  has not only forever changed how America remembers one of its first heroes — cementing the cult of Washington into the culture of the nation — but also has over the past 170 years become an icon of American history in its own right,” a description of the painting on the Christie’s website read.   Still, many scholars have pointed out inaccuracies in Leutze’s painting: For example, Washington clearly could not have, and would not have, stood up in such weather in his boat — which would have been a larger Durham boat and not the smallish rowboat portrayed in the painting. In addition, the Stars and Stripes design of the American flag didn’t exist until nearly a year after the crossing, the ice floes looked more like the kind of river ice you’d find on the Rhine and not between New Jersey and Pennsylvania.  Despite those factual errors, the importance of Washington’s crossing are hard to overstate: With the 2,400 men he carried across the Delaware on Christmas Day in 1776 and the subsequent successful surprise attack on Trenton, Washington greatly boosted the Continental Army’s morale, attracted waves of new recruits and laid the groundwork for eventual victory over the British. So, time to break out those checkbooks and start bidding!