Snake oil became a synonym for quackery thanks to the career of Clark Stanley, The Rattlesnake King. He used his experience as a cowboy to promote cures he claimed to learn from the Hopi Indians. This advertisement was featured in a promotional book, The Life and Adventures of the American Cowboy, featuring information about cowboys, snakes, and numerous advertisements for his snake oil liniment.
Courtesy of Archive.org
Image featured in Discovering Quacks, Utopias, and Cemeteries: Modern Lessons from Historical Themes by Cynthia Resor