If his subjects were purely imaginary, he rendered them with an uncommon amount of descriptive reality, staging scenes in his studio and going to nearly unbelievable lengths to assemble models and props. He once borrowed, for instance, an actual train seat from the Atchison, Topeka and Santa Fe Railway System and then mailed it back when he was done with it. He refused to sketch so much as an old wool sock without having the real version in front of him, humbly claiming that he could not draw from his imagination.

His heyday was the 1940s and early ’50s, when the accumulated sorrows of the Depression and two World Wars imbued Americans with a sense of solidarity and common purpose. “There was a strong sense of loss,” Mr. Spielberg said. “Because not since World War I had America’s mothers lost so many sons. It was an open wound, and Rockwell was part of the healing process.”

As beloved as he was by the public, he suffered the slings of critical derision, especially in the ’50s. The dominant art movements of that era — Abstract Expressionism, Beat poetry and hard bop jazz — devalued craftsmanship in favor of improvisation and the raw, unmediated gesture. Against this backdrop Rockwell was accused of purveying an artificial and squeaky-clean view of America, which remains a criticism of him today.

Image Norman Rockwell in 1921. Credit... Underwood & Underwood/The Library of Congress

It is true that his work, for the most part, does not acknowledge social hardships or injustice. It does not offer a sustained meditation on heartbreak or death. Yet why should it? Idealization has been a reputable tradition in art at least since the days when the Greeks put up the Parthenon, and Rockwell’s work is no more unrealistic than that of countless art-history legends, like Mondrian, whose geometric compositions exemplify an ideal of harmony and calm, or Watteau, who invented the genre of the fête galante. Rockwell perfected a style of painting that might be called the American Ideal. Instead of taking place in lush European gardens, his playful gatherings are in a diner on Main Street.

It took the piety-bashing ways of postmodernism to open the gates of Rockwell appreciation in the art world. Virginia M. Mecklenburg, the curator of the current exhibition at the Smithsonian, said recently that she traces that moment to 1997, when the art historian Karal Ann Marling published an admiring monograph on Rockwell for the Harry N. Abrams Library of American Art series. The book laid the groundwork for a full-scale Rockwell reconsideration that proceeded in short order. Critics awoke to the draftsmanly prowess of his work, museums like the Solomon R. Guggenheim confidently exhibited, it and prices for his paintings rose exponentially. The auction record for a Rockwell was set in 2006, when “Breaking Home Ties” — a symbol of empty-nest despair that shows an aging rancher and his son waiting for the train that will take the boy to college — was sold for $15.4 million.