"The CIO was born out of a fundamental dispute within the U.S. labor movement over whether and how to organize industrial workers...craft union...industrial union...
While the AFL had always included a number of industrial unions, such as the United Mine Workers and the Brewery Workers, by the 1930s the most dogmatic craft unionists had a strong hold on power within the federation. They used that power to quash any drive toward industrial organizing.
Industrial unionism became even more fierce in the 1930s, when the Great Depression in the United States caused large membership drops...A number of labor leaders, and in particular John L. Lewis of the Mine Workers.. started to press the AFL to change its policies in this area...
While the bureaucratic leadership of the AFL was unable to win strikes, three victorious strikes suddenly exploded onto the scene in 1934. These were the Minneapolis Teamsters Strike of 1934 led by the Trotskyist Communist League of America, the 1934 West Coast Longshore Strike led by the Communist Party USA, and the 1934 Toledo Auto-Lite Strike led by the American Workers Party...
The AFL did authorize organizing drives in the automobile, rubber and steel industries at its convention in 1934, but gave little financial support or effective leadership to those unions. The AFL’s timidity only succeeded in making it less credible among the workers it was supposedly trying to organize...
The dispute came to a head at the AFL’s convention in Atlantic City in 1935... After some more words, Lewis punched Hutcheson, knocking him to the ground; Lewis then relit his cigar and returned to the rostrum. The incident...helped cement (John L.) Lewis’ image in the public eye as someone willing to fight for workers’ right to organize.
Shortly after the Convention, Lewis called together...International Typographical Union...Amalgamated Clothing Workers of America...ILGWU...United Textile Workers...Mine, Mill and Smelter Workers Union...Oil Workers Union...Hatters, Cap and Millinery Workers to discuss the formation of a new group within the AFL to carry on the fight for industrial organizing.
The creation of the CIO was announced on November 9, 1935.
Whether Lewis always intended to split the AFL over this issue is debatable; at the outset, the CIO presented itself as only a group of unions within the AFL gathered to support industrial unionism, rather than a group opposed to the AFL itself.
The AFL leadership, however, treated the CIO as an enemy from the outset, refusing to deal with it and demanding that it dissolve. The AFL’s opposition to the CIO, however, only increased the stature of the CIO and Lewis in the eyes of those industrial workers keen on organizing and disillusioned with the AFL’s ineffective performance.
Lewis continued to denounce the AFL’s policies while the CIO offered organizing support to workers in the rubber industry who went on strike and formed the Steel Workers Organizing Committee (SWOC), in defiance of all of the craft divisions that the AFL had required in past organizing efforts, in 1936; Lee Pressman, affiliated with the far left, became the union's General Counsel...
The AFL continued to fight the CIO, forcing the NLRB to allow skilled trades employees in large industrial facilities the option to choose, in what came to be called "Globe elections," between representation by the CIO or separate representation by AFL craft unions....
http://en.wikipedia.org/wiki/Congress_of_Industrial_Organizations