Alice Waters made her first pilgrimage to Monticello in 2011. Long an admirer of Thomas Jefferson, she marveled at the gardens full of heirloom varietals, like Tennis Ball lettuce and Marseilles fig, and paid homage to the man who praised small farmers as “the most valuable citizens,” Americans who are “tied to their country and wedded to its liberty and interests by the most lasting bands.”

Then she visited the cafe.

It was overwhelmingly stocked with ultraprocessed, packaged foods: There were racks of potato chips, salty snacks and candy bars. Coca-Cola-branded refrigerators were filled with soda, juice and a rainbow of sports drinks. The few prepackaged salads looked wan at best. There wasn’t even a stove.

“I was shocked,” said Ms. Waters, the Berkeley, Calif., restaurateur and cookbook author who has inspired devotion to seasonal and organic ingredients. “Here, in this special place, the inevitable fast food had infiltrated. I had to speak up about it. Which I did.”