Farmers deserved to be heard in Washington, but there are limits to what those big rigs can do. (Photo: Patrick Frazier collection, American University Library)

On Presidents’ Day Weekend in 1979, a devastating blizzard brought Washington, D.C., to a standstill. Streets were impassable. Schools, government offices and businesses closed. At Dulles International Airport, visibility was so bad that slow-moving snowplows crashed into each other.

But there was unlikely help at hand. Thousands of farmers had rolled into town on their tractors three weeks earlier, and many had remained camped on the National Mall, refusing to leave until Congress took up their demand for financial relief. The big rigs had lumbered across the country at 15 miles per hour, or had been hauled on flatbeds — some from as far as California, many from the Midwest. It was the third straight year of increasingly angry farm protests organized by a group calling itself the American Agriculture Movement.

By 1979, though, i…