Beginning as motorbike sporting groups after World War II, the freedom of the road and riding across the country attracted a rebellious, adventurous, tough group of young people. Biker groups became biker gangs proud of living outside the norms of the traditional American family life of the 1950s. Two movies propelled the biker life: The Wild Ones in 1954 and Easy Rider in 1969. In 1969 the Hell's Angels, an especially tough and violent motorcycle gang at the time, were hired for the security force at a Rolling Stones (a rock group from England) concert in California at Altamont Speedway. A fan was killed by the Hell's Angels during the concert. This murder gained national attention and Americans suddenly realized the violence associated with biker gangs.
During the 1970s outlaw biker gangs numbered about nine hundred. The largest biker gangs were the Hell's Angels, the Outlaws, and the Bandidos. Each improved its organizational structure and learned how to plan and carry out criminal activities for profit. Their most profitable activity was drug trafficking. By the 1980s the FBI ranked bikers right behind the American Mafia as the most serious organized crime groups in the United States.
By the 1990s, the Bandidos, Hell's Angels, and Outlaws all had chapters in other countries. Hell's Angels had organizations in twenty countries and continued to expand rapidly. Biker gangs with U.S. roots were active in Canada, Europe, South America, Australia, and Africa. Sometimes rivals but often partners in criminal activities, these powerful bikers often cooperated with the South American drug cartels and the Italian Mafia. Biker gangs launder their drug money into legitimate businesses and have become very wealthy.