Final answer:
Margaret Sanger was a nurse from New York who worked with mothers in Manhattan's tenements and advocated for birth control, leading to the founding of Planned Parenthood despite legal challenges.
Step-by-step explanation:
The New York nurse and midwife who worked in the working-class tenements of Manhattan and observed the struggles of young mothers trying to provide for their growing families was Margaret Sanger. She was not only a pioneer nurse from New York but also a birth control advocate who believed that in order for women to have healthier lives and gain equal footing in society, they needed access to information about reproduction and control over it. Margaret Sanger was an essential figure in promoting the legalization of contraceptive methods and founded Planned Parenthood. Her advocacy was met with resistance as it challenged traditional views, and distributing information on contraception could incur legal penalties under the Comstock Laws. Despite this, Sanger's persistence led to the gradual acceptance of birth control, fundamentally changing the discourse surrounding women's reproductive rights and health.