NCL to address her own policies such as local hours and wages of women via data collection and activism. Kelley also served as a mentor to younger activists, such as Mary van Kleeck, who briefly worked for the Consumers League. In her work there, she built 64 Consumers Leagues to promote and to pass labor legislation. Kelley often acted as a representative to address state legislators and expanded the NCL network through women's clubs. She worked hard to establish a workday limited to eight hours. In 1907, she threw her influence into a Supreme Court case, Muller v. Oregon, an attempt to overturn limits to the hours female workers could work in non-hazardous professions. Kelley helped file the famous Brandeis Brief, which included sociological and medical evidence of the hazards of working long hours and set the precedent of the Supreme Court's recognition of sociological evidence, which was used to great effect later in Brown v. Board of Education. Her pursuit to enforce the eight hour work day for women was later declared unconstitutional by the Illinois Supreme Court in 1895 because it restricted women from making contracts for longer hours. In 1909, Kelley helped create the NAACP and thereafter became a friend and ally of W. E. B. Du Bois. She also worked to help improve child labor laws and working conditions. In 1917, she again filed briefs in a Supreme Court case for an eight-hour workday, now for workers "in any mill, factory or manufacturing establishment," in the case Bunting v. Oregon. Kelley's NCL sponsored a "Consumer's 'white label'" on clothing that restricted garment production with child labor and working conditions against state law. She led the National Consumers League until her death, in 1932. Other accomplishments In 1907 Kelley organized New York’s Committee on Congestion of Population, after which she and Mary Kingsbury Simkhovitch sponsored an exhibit on the causes and consequences of congestion and methods for alleviating it, catalyzing the first National Conference on City Planning in 1909. Kelley worked with Josephine Goldmark to provide the information organized by lawyer Louis Brandeis in what became known as the Brandeis Brief to demonstrate the harmful effects of overtime on women's health. The action helped support arguments in Muller v. Oregon in 1908, although the U.S. Supreme Court ruled against the women laundry workers in the case. Kelley also helped lobby Congress to pass the Keating-Owen Child Labor