Margret Sanger was an advocate for birth control. Her own mother went through 18 pregnancies in 22 years resulting in 11 living children. Because of the Comstock Act and other such regulations it was illegal to distribute obscene materials, particularly though the postal service. This is the same laws that lead to Victoria Woodhull's arrest. Sanger moved to England for a short time to avoid being charged. Sanger started many organizations which would later turn into Planned Parenthood.
Click here for a great podcast on the creation of the birth control pill.