For America’s GIs, returning home from World War II and integrating back into society wasn’t always easy. At a time when veterans were expected to quickly forget the war and the wider world they’d seen—and settle down into stable homes, families and jobs—motorcycles offered a sense of personal freedom and wider horizons. Biker clubs supplied the camaraderie and adrenaline rush young men had become accustomed to on the war front.

Such clubs didn’t originate at mid-century. In the early 1900s, “motor bicyclists” banded together into riding clubs for fun and support, traveling astride vehicles that resembled today’s beach cruiser bikes, but with a small, loudly thumping motor between the wheels.

Before traffic lights started to become widely used in the 1930s, these noisy, speedy new vehicles added to the chaos of the American street scene. So some cities moved to restrict their use. In response, devotees began to organize—to fight restrictions, but also to expand membership and riding events, self-regulate road racing and encourage street repair.

In 1903, just under 100 enthusiasts met in Brooklyn to form the Federation of American Motorcyclists. Two decades later, in 1924, the American Motorcycle Association emerged. That summer, the group held a 1,400-mile endurance trial that began and ended in Cleveland, demonstrating the long-range capability of the vehicles. Eager for wide acceptance, the AMA took care to promote a positive image of motorcycling, one that portrayed riders as safe, responsible, considerate citizens who "present a good appearance to the public."

World War II gave a big boost to the motorcycle industry when the U.S. military called on manufacturers Harley-Davidson and Indian to produce more than 100,000 motorcycles for the war effort. Engineering advanced quickly as motorbikes were bulked up for use on the battlefield. “Similar to tanks, planes and automobiles, motorcycles went through a number of improvements,” wrote Rachel Kline on the Vintage Veteran website.

In 1936, Harley-Davidson produced the “knucklehead” engine, bringing far more power and reliability. Harley’s WLA model, tricked out with leather saddlebags and a rifle scabbard, proved essential to the U.S. mechanized calvary and came to be known as the “Liberator.” Within a few years, returning vets in leather jackets would be rumbling around America on machines many had ridden during the war.

The largely subdued community of mainstream motorcycle enthusiasts were in for a shock when returning veterans took their army surplus Harleys to the streets of postwar America. The average age of WWII’s returning combat veterans was 27. The war had aged them, but most were still young enough to challenge social norms. **“**Many returning combat vets reported feelings of restlessness and a general malaise,” wrote Richard Kolb in Veterans of Foreign Wars Magazine.

Much cheaper than cars, motorcycles afforded veterans a freewheeling mode of group transportation at a time when fitting back into society posed certain challenges.

“It seems logical that the horrors of war and the hell of combat may have melted down the prewar personalities of these men, only to recast them forever in a new form,” wrote scholar William Dulaney in a research study titled “Over the Edge and into the Abyss: The Communication of Organizational Identity in an Outlaw Motorcycle Club.”

“Veterans," wrote Dulaney, "searching for relief from the residual effects of their wartime experiences, started seeking out one another just to be around kindred spirits and perhaps relive some of the better, wilder social aspects of their times during the war.”

The fashion style of choice for these bikers, and for future generations, originated with the flight jackets of returning WWII airmen. Resilient wind- and rain-resistant leather, which could keep a rider warm and dry in extreme weather, became a natural choice for many motorcyclists.

The image of dangerous biker gangs on big, blatting motorcycles entered the popular imagination in full force following a “riot” on July Fourth weekend in 1947 in Hollister, California. By this time, veterans’ riding clubs like the Boozefighters were on the scene, flagrantly disregarding the wholesome image espoused by the AMA, which had organized a ride for its membership through Hollister that holiday. The town of 5,000 was overwhelmed by 4,000 riders, some of whom fell into drunken brawling. Street racing and fighting led to about 50 arrests. “Outlaw” biker clubs in attendance (ie. those not sanctioned by the AMA) included the Pissed Off Bastards of Bloomington, the Market Street Commandos, the Top Hatters Motorcycle Club and the soon-to-be infamous Boozefighters.

Coverage in the San Francisco Chronicle depicted “pandemonium.” A photo of Boozefighter Eddie Davenport, sitting on a Harley surrounded by empty beer bottles, became emblematic of what one witness called “just one hell of a mess.”

Public outrage turned to fascination. In 1953, actor Marlon Brando became the poster boy for anti-social biker behavior in the Hollywood film The Wild One, portraying gang leader Johnny Strabler. When a young woman asks, “What are you rebelling against, Johnny?”, Strabler spits back: “Whaddaya got?”. The screenplay for The Wild One had its origins in Hollister: Filmmakers based it on a 1951 Harper‘s Magazine short story by Frank Rooney titled "The Cyclists' Raid," a fictionalized account of the infamous July Fourth brawling in Hollister.

Since that time, numerous “outlaw motorcycle gangs” have sprung up across America, including the notorious Hells Angels, founded in 1948 and now considered a crime syndicate by the Department of Justice. The DOJ estimates that more than 300 outlaw motorcycle gangs, including the Bandidos, the Mongols and the Sons of Silence, are active in the U.S., asserting that many engage in drugs and weapon trafficking.

Still, while the outlaw image remains, many veterans’ motorcycle clubs today are structured as nonprofit organizations devoted to helping society with fundraising rides for good causes. But the roar of their tailpipes as they pass through town has become an enduring part of American culture, one that may never fully shed its outsider reputation.