It's an odd ritual, antique almost, with roots linked to the Vietnam War and the political passions that roiled the country during that conflict, and after.
Now, it's thousands of men and women on motorcycles on Memorial Day weekend.
On Sunday of this holiday weekend, hundreds of thousands of bikers took part in what is called - and incorporated - as Rolling Thunder. It used to be Operation Rolling Thunder, named for the bombing campaign against North Vietnam in 1965.
Rolling Thunder was established in 1968 by a pair of Vietnam veterans who wanted to hold the government accountable for the fate of U.S. prisoners of war and those missing in action in southeast Asia. At the initial rally on Capitol Hill, they announced their arrival with the roar of Harley-Davidsons.
You could say it caught on. What evolved was an annual "Road to Freedom" rally and a Washington ritual that, in time, ended at the Vietnam Veterans Memorial Wall.
That was then. Rambo was big. Chuck Norris, too. The political class embraced the bikers, inviting them to the White House. But by the early 1990s, many people bemoaned the fact that the POW-MIA issue had effectively disappeared from the American consciousness.
Now, well, you could say the same thing about the Vietnam War. We're not much on memory, despite our claims to the contrary. Vietnam was going to change everything, remember, like the fall of the Berlin Wall and 9/11.
We were going to be a more serious country, not a country where millions of people spent their evenings voting on the fate of talentless singers and hoofers on television. Maybe next time.
The disappearance of the POW-MIA issue should have ended Rollling Thunder, but it didn't. Maybe it was simply the roar of the bikes. The political environment has changed but the staging has not.
On Sunday of Memorial Day weekend, thousands of bikes roll through northern Virginia into Washington along Route 66, choking three lanes of the interstate heading east. As they do, people in neighborhoods like mine in Arlington gather on the overpasses and bridges to greet them, kids and parents waving, bikers waving back, horns tooting and - for the better part of two hours - that all-American Harley roar rending the suburban air.
Families make the effort, parking the SUVs and minvans on the bridges, carrying their coffee, minding the kids against the bridge traffic, smiling at the wall of noise. You see American flags on some of the bikes and even a few ghostly black POW-MIA flags fluttering.
By mid-day Sunday, the bikes are gone from Route 66, across Arlington Memorial Bridge hard by the cemetery. The folks in the neighborhoods are back home; the bikers are at the war memorials. Years ago they used to gather by the hundreds at a two-story beer bar on 19th Street in DC called the Crow's Nest, their bikes shoe-horned into the bar's small parking lot like some Quentin Tarantino fantasy. Pretty sure there's a Kinkos there now.
At this point it seems hard to determine what Rolling Thunder means. But the appeal of the bikes and the bridges and overpasses remains, a constant of Washington's Memorial Day.