Final answer:
Margaret Sanger and Katherine Dexter McCormick formed the American Birth Control League, known today as Planned Parenthood, advocating for women's reproductive rights and birth control.
Step-by-step explanation:
Margaret Sanger worked with Katherine Dexter McCormick to build the American Birth Control League, which is now known as Planned Parenthood. Active in poor and immigrant communities, Sanger aimed to improve standards of living by advocating for the control of pregnancies, especially for families that couldn't afford more children. This was a radical notion at the time and often brought her into conflict with laws such as the Comstock Laws, which deemed the distribution of contraceptive information as obscene. Despite the controversies, Sanger is recognized for her pioneering role in the birth control movement and her efforts to give women more control over their reproductive health.