A 1902 boycott in New York, where women, mostly housewives, boycotted kosher butchers over the price of kosher beef, caught the attention of William English Walling. Walling, a wealthy Kentucky native living at the University Settlement in New York, thought of a British organization he knew a bit about: the Women's Trade Union League. He went to England to study this organization to see how it might translate to America.
This British group had been founded in 1873 by Emma Ann Patterson, a suffrage worker who was also interested in issues of labor. She had been, in her turn, inspired by stories of American women's unions, specifically the New York Parasol and Umbrella Makers' Union and the Women's Typographical Union. Walling studied the group as it had evolved by 1902-03 into an effective organization that brought together middle-class and wealthy women with working-class women to work for improved working conditions by supporting union organizing.
Walling returned to America and, with Mary Kenney O'Sullivan, laid the groundwork for a similar American organization. In 1903, O'Sullivan announced the formation of the Women's National Trade Union League, at the annual convention of the American Federation of Labor. In November, the founding meeting in Boston included Boston settlement house workers and AFL representatives. A slightly larger meeting, November 19, 1903, included labor delegates, all but one of whom were men, representatives from the Women's Educational and Industrial Union, who were mostly women, and settlement house workers, mostly women.
Mary Morton Kehew was elected the first president, Jane Addams the first vice-president, and Mary Kenney O'Sullivan the first secretary. Other members of the first executive board included Mary Freitas, a Lowell, Massachusetts, textile mill worker; Ellen Lindstrom, a Chicago union organizer; Mary McDowell, a Chicago settlement house worker and experienced union organizer; Leonora O'Reilly, a New York settlement house worker who was also a garment union organizer; and Lillian Wald, settlement house worker and organizer of several women's unions in New York City.
Local branches were quickly established in Boston, Chicago and New York, with support from settlement houses in those cities.
From the beginning, membership was defined as including women trade unionists, who were to be the majority according to the organization's by-laws, and "earnest sympathizers and workers for the cause of trade unionism," who came to be referred to as allies. The intention was that the balance of power and decision-making would always rest with the trade unionists.
The organization helped women start unions in many industries and many cities, and also provided relief, publicity, and general assistance for women's unions on strike. In 1904 and 1905, the organization supported strikes in Chicago, Troy and Fall River.
From 1906-1922, the presidency was held by Margaret Dreier Robins, a well-educated reform activist, married in 1905 to Raymond Robins, head of the Northwestern University Settlement in Chicago. In 1907, the organization changed its name to the National Women's Trade Union League (WTUL).

