A new government report says the rate of smoking among adults fell to 15 percent last year.
A survey conducted by the Centers for Disease Control and Prevention says that's the biggest decline in more than 20 years.
About 50 years ago, roughly 42 percent of adults smoked.
Experts say it's because of anti-smoking advertising campaigns, cigarette taxes and smoking bans. They say that the growing popularity of electronic cigarettes has also likely played a role.
Smoking is the nation's leading cause of preventable illness, causing more than 480,000 deaths each year in the United States, the CDC estimates.