Abortion was legal under common law in the United States leading up to the 19th century. Early laws only prohibited the use of toxic substances to cause miscarriages after "quickening," or when a woman feels her child move -- usually four or five months into the pregnancy.

During the Great Depression the dangerous practice of unregulated abortions led to a high U.S. maternal mortality rate. A study done in 1931 showed illegal procedures were responsible for 14% of maternal deaths.

In 1969 a group of young women in Chicago started "Jane," an underground system that helps women find safe and affordable illegal abortions. Eventually they learn to perform the procedures themselves, completing nearly 12,000 abortions from 1969 to 1973, according to a documentary about the group.

Source: When Abortion Was A Crime by Leslie J. Reagan (Author) http://www.ucpress.edu/book.php?isbn=9780520216570