From May to August of 1934, Minneapolis was rocked by a strike that would forever change the course of U.S. labour history. This was the strike of Teamsters Local 574, a union led by Trotskyists. Many of the best techniques used by organised labour today find their origins in the Minneapolis Strike, in particular the flying picket. However, the strike's greatest conquest was in laying the foundations for industrial unionism in North America, leading to the formation of the Congress of Industrial Organizations (CIO) in the following years. Above all, the Minneapolis Strike demonstrated the role played by the young forces of American Trotskyism in obtaining gains for workers.