WEDNESDAY, Nov. 17 (HealthDay News) -- Get ready, get set, quit! Thursday marks the annual Great American Smokeout, sponsored by the American Cancer Society, which urges all smokers to lay off the habit for at least 24 hours.

There have been dramatic changes in attitudes about smoking and a large decrease in smoking rates since the Smokeout was first held in 1977.

The annual event includes local and nationwide events meant to encourage smokers to quit for at least one day in the hope that they may decide to permanently kick the habit.

The Smokeout has helped focus attention on the dangers of tobacco use and contributed to a "cultural revolution" in tobacco control, says the American Cancer Society.

Between 1978 and 2009, the percentage of adults who smoke in the United States fell from 34 percent to 21 percent, according to the U.S. Centers for Disease Control and Prevention (CDC).

Smoking is now banned in many public places and work areas. As of Oct. 1, 2010, Medicare programs must cover tobacco-dependence treatments for pregnant women. Beginning in 2011, coverage for smoking cessation treatment will be provided to all federal employees, retirees, and their spouses and dependents.

But, even though progress is being made, 46.6 million U.S. adults still smoke, 40 percent of nonsmokers are exposed to secondhand smoke, and smoking and secondhand smoke causes 443,000 deaths each year, according to the CDC.

That's why the Great American Smokeout is still important. Thousands of volunteers visit schools, malls and workplaces to distribute information about quitting and to publicize events. The volunteers also enlist nonsmokers to "adopt" smokers for the day and support them with advice and snacks.

Smokers who take part are asked to quit smoking for 24 hours. Even if they don't quit permanently, they learn that they can kick the habit for a day and that they have plenty of support if they decide to quit in the future, according to the American Cancer Society.

The day includes events such as parades, rallies, athletic activities and ceremonial cigarette burials and bonfires. Some unique events from previous years include:

• A national sandwich shop handed out free "cold turkey" sandwiches and cookies to smokers who traded in at least a half pack of cigarettes.
• A hospital gave newborns free T-shirts that said "I'm a Born Nonsmoker."
• A Houston event used the slogan "Don't Let Smoking Be an Obstacle" for an activity in which smokers ran an obstacle course that included oversized cigarette packs, matches and ashtrays.

More information

Here's where you can learn more about the Great American Smokeout.