During the Progressive Era, reformers sought to improve working conditions for women, most of whom worked long hours for little pay in dangerous conditions. Women had few options because male unions did not admit women and it was difficult for women to organize and successfully bargain on their own. Many reformers believed that protective labor legislation was the best option and began to lobby for protective laws. Some women opposed protective labor laws because they believed that these laws would harm women workers by making it more difficult for women to fully realize their rights. Those supporting protective laws argued that legislation for women was just the first step towards legislation that would protect all workers.
The Pennsylvania Superior Court was the first to introduce women's distinct role as child bearers into an analysis of a protective labor law: It upheld a state law limiting the hours adult women could work, affirming a lower court decision which noted that the act prevented the "mothers of our race" from endangering their health with exhaustive employment. This set the tone for more than sixty years worth of legislation aimed at protecting women and shaped the legal strategies employed by reforms in defending protective labor legislation. In Muller v. Oregon, the Supreme Court upheld an
Oregon law that limited women's working hours to ten a day. A women's reform group had submitted an amicus brief claiming that the law was trying to prevent the negative impact long work hours have on women's health and reproductive functions. They argued that the state had a definable interest in maintaining women's social function, while long hours would compromise women's reproductive role and social role as mothers. The court noted that the differences between men and women were general knowledge. Because women were physically inferior they deserved protection, and while not all women would be mothers, women's reproductive potential was enough to justify a state interest. Women's differences put them in a separate class that could be regulated by protective legislation.
There were several arguments that could have been used to defend protective legislation, but the motherhood rationale came to dominate the jurisprudence. Women's stature, physical abilities, and capacity to bear children were all cited in support of protective legislation. Courts also relied on assumptions about women's role in society. Men were seen as rights-bearing wage earners, while women were supplementary wage earners whose real job was to serve in the home, and remain financially dependent on their husbands. This reasoning was used to exclude women from a number of occupations and limit their participation in the workplace.
Although Muller is no longer good law, the courts continued to view men's and women's employment as distinct for many years. This view was accepted until 1991, when Johnson Controls v. UAW concluded that employers could not decide whether a woman's reproductive role was more important to her than her family. This overruled the legal ideology of motherhood and recognized women's place in the market as rights-bearing wage earners.||en-US