The American Federation of Labor (AFL) tried and failed to organize the steelworkers in 1919.  Although the strike gained widespread middle-class support because of its demand and the 12-hour day, the strike failed and unionization was postponed until the late 1930s. The mills ended the 12-hour day in the early 1920s.
The second surge of unionization came under the auspices of the militant Congress of Industrial Organizations in the late 1930s, when it set up the Steel Workers Organizing Committee. The SWOC focused almost exclusively on the achievement of a signed contract, with "Little Steel" (the major producers except for US Steel).  At the grassroots however, women of the steel auxiliaries, workers on the picket line, and middle-class liberals from across Chicago sought to transform the strike into something larger than a showdown over union recognition. In Chicago, the Little Steel strike raised the possibility that steelworkers might embrace the ‘civic unionism’ that animated the left-led unions of the era.  The effort failed, and while the strike was won, the resulting powerful United Steelworkers of America union suppressed grassroots opinions.