DARTMOUTH COLLEGE — This is the story of two men, a radical Mexican muralist and a conservative college president, who shared “an American idea.” The idea was the value of open minds. Embraced by the unlikely pair, the idea left this college with a masterpiece and a lesson in “liberal arts.”

As a liberal arts colleges go, Dartmouth is rather conservative. Founded by a minister, chartered by a king, the New Hampshire college seems as buttoned-down as its brick facades. Dr. Seuss went here, as did TV’s Mr. Rogers but alumni also include 164 Congressmen, three cabinet members, and countless CEOs. Dartmouth also hosted the fraternity made notorious in “Animal House.”

But walk into the Baker Library, past students staring into phones, and head downstairs. . . There in the basement stands, one art historian claimed, “the most significant mural decoration ever made in our country.”

“The Epic of American Civilization” begins with towering bronzed Aztecs. It ends with capitalists in top hats gobbling up coins. In between lie revolution, skeletons, snakes, and Pancho Villa. Over in one corner is a signature — J.C. Orozco, February 13, 1934.

During the depths of the Depression, Jose Clemente Orozco came to Dartmouth from his native Mexico. The Baker Library was new and needed decoration. Orozco was paid $500 in Rockefeller money (Nelson Rockefeller was a Dartmouth alum) to show students how Mexican artists were reviving the art of fresco — paint applied to wet plaster.

Short and stocky, with thick glasses, Orozco looked as bookish as the students who watched him work from his wooden scaffold. But he had survived an impoverished childhood and the bloody Mexican Revolution. “The world was torn apart around us,” he remembered. “Troop convoys passed on their way to slaughter. Trains were blown up.”

The Revolution turned Orozco into a political painter making “art at the service of the Worker.” So when he began painting his fiery epic, old Yankee money was (ahem!) concerned.

A group calling itself Boston Mothers wrote to Dartmouth’s president. Shouldn’t the college “do as much as possible to uplift” students? Why not decorate the library with “beautiful scenery. . . rather than hideous subjects?” Another letter was less polite: “Orozco has shouted forth in paint the Communist Manifesto!”

Dartmouth’s president knew that Orozco was “a flaming red communist.” Yet Ernest Hopkins was not afraid of ideas. Hopkins had toiled in granite quarries before using his own Dartmouth education to enter business. He had come to believe “it was not the form of a man’s activity or even his association which defined either good or bad citizenship but rather what was the nature of the man himself.” Now the lifelong Republican defended the “communist.”

Responding to the Boston Mothers, Hopkins wrote, “There are 100% Americans who have objected to the fact that we employed a Mexican to do this work, but I have never believed that art could be made either racial or national.” As to the images not being “nice,” “if that be a criterion of judgment many of the great works of the medieval masters would have to be removed from the Louvre.”

Month after month, Orozco applied paint to plaster. He painted cannons and chains. Huddled masses. Grisly “Gods of the Modern World.” As Orozco worked in a library basement, the more celebrated Diego Rivera was painting at Rockefeller Center in Manhattan. But when Rivera put Lenin on one wall, he was fired. The mural was destroyed. Back at Dartmouth, Orozco kept working.

“The position Dartmouth was taking,” he remembered, “expressed one of the most highly prized of American virtues: freedom — of speech and thought, of conscience and the press — the freedoms of which the American people have always been justifiably proud.”

The Mexican artist spent two years in the New England town. He found Dartmouth “delicious in winter.” The woods, the snow, the “country folk.” Students got him to judge an ice sculpture contest, an art he found “stupendous.” Faculty welcomed him to classes. And when he finished, they threw him a gala dinner. There the college president toasted to Orozco’s “AMERICAN idea developed into American forms, American feeling, and as a consequence, into American style.”

Today, students at the Baker Library pay scant attention to “The Epic of American Civilization.” They come and go, chatting, staring into phones. But here in the basement, what one art historian called “a great jeweled cup overflowing its conventional brim,” is more than a masterpiece. It is a tribute to an American idea that has not dried into plaster.

THE CONSERVATIVE AND THE 'COMMIE'