Hillman was born to a family of rabbis and small business owners in Lithuania in 1887. He arrived in the United States in 1907. By the age of sixteen he was organizing the typesetters of Kovno for the Bund, the outlawed Jewish trade union movement. The Czarist police imprisoned him in 1904 for organizing in a labor parade, and again during the revolution of 1905 while working for the Social Democratic party. When the revolution was defeated he fled to the United States. In Chicago he worked for $8 a week as a cutter at the giant the men's clothing factory of Hart, Shaffner and Marx. In 1910 the workers there went on strike, sparking a strike in the entire Chicago men's clothing industry. Hillman became a strike leader and negotiated a compromise settlement calling for arbitration. He was elected business agent of the newly formed Local 39, United Garment Workers of America. His moderation and realism now made the arbitration plan work, as Hillman gained the trust of workers and management. Meanwhile, a new national union formed of needle workers, the Amalgamated Clothing Workers of America. It named Hillman president and became his base of power until his death.
The Amalgamated could not join the AFL, which recognized its rival the more established United Garment Workers.
The breakthrough came with World War I: the military needed uniforms fast, and the Amalgamated, after winning several bloody strikes in Chicago and Baltimore, was an all-out supporter of the war effort. Hillman shrewdly mixed militancy and reasonable negotiation, and added a new dimension with his cooperation with the new federal Board of Control and Labor Standards for Army Clothing. By 1920 the Amalgamated enrolled 177,000 dues paying members, with contracts covering 85% of the men's clothing industry. The Amalgamated forced companies to stop using sweatshops (that is, families working in their own apartments for much lower pay), and achieved the forty-four-hour week by 1920.
Hillman disagreed with the strategy of the AFL to concentrate on skilled workers. He believed in "industrial unionism", which involved unionizing all he workers in an industry of all skill levels. He was quite successful with this approach to clothing workers; John L. Lewis was developing a similar approach at the same time regarding coal miners. Hillman and Lewis, however, had a deeper strategy. They saw that industries like sewing and coal mining were dominated by hundreds of small firms, that engaged in ruinous competition. Wage comprised most of the cost of doing business in the needle trades and coal mining, so brutal competition meant lower wages. The way to improve conditions, raise wages and raise profits was to have the union control the industry by setting high wages. In a competitive marketplace, other firms were helpless when a competitor cut prices—they had to follow. But if the union policed the industry and prevented wage cuts and thus price cuts, then cutthroat competition with low wages and low wages would be impossible. The solution only worked in a few industries (especially clothing and coal) where conditions were exactly right (many small companies, wages the biggest expense.) These conditions did not apply in most industries. The problem in the 1920s was that unions were too weak to police their industries, so when the New Deal arrived in 1933, Hillman jumped at the chance to have the NRA police the industries and keep wages high. When NRA ended in 1935, Hillman helped Congress pass the Wagner Act which greatly facilitated union membership drives.
The AFL finally admitted Amalgamated in 1933, but by 1933 Hillman and Lewis threw their unions behind a new venture, the CIO (at first named the "Committee for Industrial Organization") with the dream of industrial unionization for all of America. Both the CIO and AFL unions strongly supported Roosevelt's landslide reelection in 1936, with Hillman heading the CIO campaign committee. The AFL in 1937 expelled the CIO (now renamed the "Congress of Industrial Organizations"), and the two federations spent much of 1937-40 fighting each other for membership in industries such as meatpacking and electrical equipment. Both grew rapidly. The Amalgamated itself reached 300,000 members, and operated its own banks, housing developments, and unemployment insurance system.
In 1940 Lewis broke with Roosevelt over foreign policy and Hillman became FDR's chief labor spokesman, and CIO members, listening to Hillman not Lewis, voted 85% for FDR in 1940. In 1940-41 as the nation rearmed rapidly, Hillman handled labor affairs for the government, which involved rapid expansion of munitions industries and unionization of the new workers. In early 1942 he was pushed out of power in Washinton and returned to New York to direct the Amalgamated and fight for FDR's reelection.
Hillman was never a Communist Party member. He understood the Communist Party and its methods and would not permit his union to be controlled by the Party. The membership of his union was overwhelmingly Socialist who lived within the capitalist system.
The Congress of Industrial Organizations (CIO) depended on Communist organizers for its rapid growth. Hillman knew Michael Quill, Joseph Curran, Harry Bridges, Richard Frankensteen, Walter Reuther, Ben Gold, Abram Flasner and numerous other leaders who had moved into the CIO were Communists or fellow travelers (that is a person who supported Communist policies but did not join the Party). Hillman understood Communists in labor unions are not interested in the welfare of the members but in the use of the union apparatus for pro-Soviet activities; he supported Roosevelt's use of Army troops to break up a strike at North American aviation in June 1941.
Hillman was one of many labor leaders to use the goon as part of his enforcement machinery.
"Clear It with Sidney"
Hillman in 1943 set up 1943 the CIO Political Action Committee (PAC) to mobilize voters in the 1944 elections. At the 1944 Democratic National Convention, Hillman and the CIO supported leftist Henry A. Wallace for renomination as Vice President; Senator Harry Truman was their second choice. Roosevelt, however, had given up on Wallace, who had failed in his wartime roles, and told the Democratic Chairman Bob Hannegan, "Go on down there and nominate Truman before there's any more trouble. And clear it everything with Sidney."  Republicans used the slogan "Clear it with Sidney" to hammer away at the allegation that the president was a pawn in union control.
The Democrats could win the Presidential election of 1944 if they could carry the Southern states and in addition New York, Massachusetts, Illinois, Michigan and New Jersey. These states were strongholds of the CIO, which had 5 million members. Hillman's Political Action Committee (PAC) put the manpower on the sidewalks of industrial America and turned out the voters, as Roosevelt narrowly won a fourth term
Hillman, in poor health for years, died suddenly of a heart attack in 1946 at age 59.
- Bernstein, Irving. Turbulent Years: A History of the American Worker, 1933-1941 (1970), the best overview of the era
- Fraser, Steve. Labor Will Rule: Sidney Hillman and the Rise of American Labor (1993). excerpt and text search, the standard scholarly biography
- Fraser, Steve. "From The 'New Unionism' To The New Deal." Labor History 1984 25(3): 405-430. 0023-656x online
- Galenson, Walter. The CIO Challenge to the AFL: A History of the American Labor Movement, 1935-1941 (1960) online editiononline edition
- Josephson, Matthew. Sidney Hillman (1952), good older biography
- Lichtenstein, Nelson. Labor's War at Home: The CIO in World War II (2003)
- Zieger, Robert H. The CIO, 1935-1955 (1995) online edition, the standard scholarly history
- Communists in the miners union supported Russia and its ally Germany in 1940, and strenuously opposed FDR's efforts to help Britain fight Germany. Lewis went along with the Communists and attacked FDR.
- "Clear everything with Sidney", Time, Sep. 25, 1944.
- See "The New Force", Time, Jul. 24, 1944.
- Vladimir I. Lenin to Sidney Hillman, Lenin Collected Works, Progress Publishers, 1976, Moscow, Volume 35, pages 526-527.