Editor's note: Nicolaus Mills is professor of American studies at Sarah Lawrence College and is at work on a history of the last decade, "Season of Fear: American Intellectuals and 9/11."
(CNN) -- Spend any time with Occupy Wall Street, as I have during the last two weeks, and you come away believing the movement is here for the long run. In New York, where I live, they have made a home out of Zuccotti Park. The park, which is dominated by honey locust trees and a 70-foot-high, red-steel Mark di Suvero sculpture, is just one block square in size, but Occupy Wall Street has made inching through the park and its overflow crowds feel like being at an old-fashioned family picnic.
The challenge Occupy Wall Street offers to Washington politics has caught media observers by surprise. It defies their assumptions that a movement without formal leaders or lots of money to publicize itself can't make a difference. But it is a mistake to think Occupy Wall Street is without historical roots. It joins a long list of political movements that have made their cause known by occupying public space.
The best-known early example was Coxey's Army, which in 1894 marched down Pennsylvania Avenue and briefly occupied the Capitol grounds. Led by Jacob Coxey, a quarry owner from Massillon, Ohio, the men and women of Coxey's Army, who called themselves the "Commonweal of Christ," sought to get Congress to end unemployment with legislation authorizing road building and other internal improvements. Coxey was eventually arrested, his army dispersed, but they set a precedent for how to get the attention of Congress and the media.
More than three decades later, in the early years of the Great Depression, a group of World War I vets, the Bonus Marchers, adopted a similar strategy. In 1932, they came to Washington, asking to have immediate payment of their Adjusted Service Certificate -- their bonus, as they called it.
Unable to get Congress and President Herbert Hoover to act, the Bonus Marchers set up camp in downtown Washington and along the Anacostia River in the hope that their presence would change hearts.
The Bonus Army was unsuccessful in 1932. The U.S. Army, led by Gen. Douglas MacArthur, routed them with tear gas, destroying the shantytowns they had set up. But in 1933, 1934 and 1935, when the Bonus Marchers came back to Washington, the Roosevelt administration let them stay at an Army post in Virginia and supplied them with tents and food. It was the start of a new day for the vets, and in 1936 Congress at last voted them their bonus.
By the '60s and '70s, when Vietnam War protests began bringing large numbers of demonstrators to Washington, the precedents established by Coxey's Army and the Bonus Marchers were a dim memory for most Americans, but the strategy of trying to change government policy by occupying Washington once again prevailed. The most dramatic attempt occurred in the spring of 1971 when May Day protesters sought to bring the city to a halt by blocking key bridges and streets.
The protesters failed to shut down Washington, but they made clear that the government could not wage war in Vietnam and have peace at home. Keeping traffic flowing in Washington came at a high price. On the first day of the protests, 7,000 were arrested, and before the protests were over, the D.C. police had so many in custody that they had no room for them in the city's jails. The only alternative for the police was to move those arrested to a fenced-in yard at Robert F. Kennedy Stadium.
For Occupy Wall Street, the good news is the political tradition to which it is linked is not one that requires imitation. There is every reason for Occupy Wall Street to continue to make its particular focus a state of mind rather than the kind of specific goal for which the Bonus Marchers and the May Day protesters strived.
For orthodox politicians that strategy is, to be sure, maddening. They are left with no clear grounds for calling an end to Occupy Wall Street. Walking through Zuccotti Park on Sunday, I thought of my own involvement in the 1971 May Day protests and recalled being shocked that after getting pepper sprayed, I was unable to continue blocking the small section of Dupont Circle the group I was with had been assigned.
How much more flexible Occupy Wall Street is from the way we were. Our chief poster consisted of a stylized drawing of Gandhi sitting cross-legged with his right fist in the air. Occupy Wall Street has no equivalent poster. Its prevailing motif may be "We Are the 99%"-- a reference to the richest 1% of the country, but the highly personal combination of wit and politics of the Occupy Wall Street posters is their distinguishing feature.
From an ironic Ronald Reagan reference, "Mr. Obama, Tear Down this Wall," to a police-friendly "Every cop is one of the 99%," the posters reflect a movement that refuses to limit itself to a single, concrete goal, even when its elders say it cannot remain fluid indefinitely.
The opinions expressed in this commentary are solely those of Nicolaus Mills.