He began the study of medicine at Wheeling, Virginia (now part of West Virginia) in 1842, but soon afterward moved to New York City, and graduated from the New York College of Physicians and Surgeons in 1846. He was then appointed assistant at Bellevue Hospital, and subsequently was the first resident physician at Blackwell's Island. He afterward resigned and visited Europe, but in 1853 was reappointed.

During his second seven years' tenure of the office of resident physician, he was asked by the New York City alderman to look into the motives of prostitutes. He oversaw police interviews of 2000 women at Blackwell's Island. The results of his study he embodied in a work characterized by laborious research and comprehensive classification of the facts that he obtained, entitled the History of Prostitution (New York, 1858). In 1860, Sanger resigned and devoted the remainder of his life to private practice.

• This article incorporates text from a publication now in the public domain: Wilson, J. G.; Fiske, J., eds. (1900). "Sanger, William Wallace" . Appletons' Cyclopædia of American Biography. Vol. Supplement. New York: D. Appleton.
• Martin, Melissa Ellis (2006). "Sanger, William Wallace". In Melissa Hope Ditmore (ed.). Encyclopedia of Prostitution and Sex Work. Vol. 1. Greenwood Publishing Group. pp. 424–425. ISBN 9780313329685.

• Works by William Wallace Sanger at Project Gutenberg
• Works by or about William Wallace Sanger at Internet Archive
• Works by William Wallace Sanger at LibriVox (public domain audiobooks)  
• The history of prostitution: its extent, causes and effects throughout the world. New York: The Medical Publishing Co. 1910.