Jackson Pollock’s first large-scale painting, Mural, was commissioned by Peggy Guggenheim in 1943, for the entry hall of her Manhattan townhouse. Paint seems to stampede the canvas, epic at eight feet high and 20 feet wide. “Every animal in the American West,” Pollock later said, was “charging across that goddamn surface.” Not literally. This pivotal masterpiece of abstraction hasn’t been on view in New York in over 20 years. —L.J.