It’s no surprise that progressives at the turn of the twentieth century supported minimum wages and restrictions on working hours and conditions. Isn’t this what it means to be a progressive? Indeed, but what is more surprising is why the progressives advocated these laws. A first clue is that many advocated labor legislation "for women and for women only."
Progressives, including Richard Ely, Louis Brandeis, Felix Frankfurter, the Webbs in England etc., were interested not in protecting women but in protecting men and the race. Their goal was to get women back into the home, where they belonged, instead of abandoning their eugenic duties and competing with men for work.
Unlike today’s progressives, the originals understood that minimum wages for women would put women out of work – that was the point and the more unemployment of women the better!
Much more on the secret history of the minimum wage in Tim Leonard‘s paper, Protecting Family and Race: The Progressive Case for Regulating Women’s Work.