The International Ladies' Garment Workers' Union (ILGWU) was founded in New York City in 1900 in an effort to consolidate the power of the various garment trades into one collective force. The history of garment workers in general and of the nascent organizing efforts of the ILGWU in the early 20th century is plagued with tragedy, most well-known being the Triangle Shirtwaist Factory fire of 1911 that claimed the lives of 146 workers who were locked into the factory and could not escape when a fire broke out. However, despite difficult conditions the ILGWU was hugely successful through work stoppages and strike campaigns in organizing large masses of garment workers in New York and around the country, establishing better working conditions and shorter working hours. In 1909, shirtwaist workers revolted in what was known as the "Uprising of 20,000" that eventually won the 52-hour work week. Over the next decade, strikes all over the country continued to win better conditions for garment workers. In 1913, the Union Health Center was established in New York City and provided decent and urgently needed health care for union members. Due to internal strife involving communist and anti-communist leadership, hardening economic conditions as well as anti-union efforts, the ILGWU and its membership suffered through the 1920s. Roosevelt's presidency and better labor laws brought a resurgence to organizing. David Dubinsky became president of the union in 1932 and served until 1966. Under Dubinsky's leadership, the union helped establish the Congress of Industrial Organizations, but eventually disaffiliated with them and went back to the American Federation of Labor in 1940. The ILGWU was a trailblazer in terms of providing education for workers, The Union's Education Department was vibrant, churning out pamphlets and publication on union history, membership and leadership. The ILGWU established social centers, offering numerous educational, community and athletic activities for its membership. Communism and corruption continued to be major sources of internal struggle for the ILGWU through the 1950s.

In July 1995 the ILGWU merged with the Amalgamated Clothing and Textile Workers Union (ACTWU) at a joint convention, forming UNITE (Union of Needletrades, Industrial and Textile Employees). Then in 2004, UNITE and the Hotel Employees & Restaurant Employees International Union (HERE) merged to form Unite Here.