Members of the Centro de Trabajadores Unidos en la Lucha (Center of Workers United in Struggle, CTUL) rally to support retail cleaning workers and their legal fight to collect unpaid wages from big-box employers like Target and K-Mart, 2014. Used with the permission of CTUL; photographer unknown.

Labor Day Parade, Nicollet Avenue, Minneapolis, 1909.

Demonstration, led by 15 Now Minnesota, for higher pay and better working conditions at the Minneapolis-St. Paul International Airport, December 2014. Photograph by Ginger Jentzen; used with the permission of Ginger Jentzen.

Men swinging bats and sticks during clash between striking truckers and a citizens’ army, Minneapolis, May 21, 1934. Pictured in the foreground are Basil Hurt, Merle Kerr, and Frank Vocks.

Workers striking at Hormel Packing Plant, Austin, 1933.

Strike at Hormel Packing Plant, Austin. Photograph by the St. Paul Daily News, 1933.

A Farmer-Labor political poster atop an automobile, ca. 1925.

Labor Day Parade, Nicollet Avenue, Minneapolis, 1909.

United Garment Workers Union members in a horse drawn carriage on Labor Day, St. Paul, 1905.