The Great American Smokeout is a social engineering experiment that encourages people to quite smoking. Lynn Smith, the publisher of a Minnesota newspaper, introduced the concept in 1974 when she announced a “Don’t Smoke Day” or “D-Day.”

Today, the Great American Smokeout is sponsored by the American Cancer Society. On the third Thursday of November, smokers across the country try to give up their cigarettes for 24 hours. The idea is that many will quit smoking altogether. Learn more about the harmful effects of tobacco and how to participate in this year's festivities.