Mary Coffin Ware Dennett was an American women's rights activist, pacifist, homeopathic advocate, and pioneer in the areas of birth control, sex education, and women's suffrage. She co-founded the National Birth Control League in 1915 together with Jessie Ashley and Clara Gruening Stillman. She founded the Voluntary Parenthood League, served in the National American Women's Suffrage Association, co-founded the Twilight Sleep Association, and wrote a famous pamphlet on sex education and birth control. A famous legal case against her eventually became the catalyst for overturning the Comstock laws.

The Comstock laws are a set of federal acts passed by the United States Congress under the Grant administration along with related state laws. The "parent" act was passed on March 3, 1873, as the Act for the Suppression of Trade in, and Circulation of, Obscene Literature and Articles of Immoral Use. This Act criminalized any use of the U.S. Postal Service to send any of the following items: obscenity, contraceptives, abortifacients, sex toys, personal letters with any sexual content or information, or any information regarding the above items.