Tobacco is currently grown in 16 states in the United States. The largest tobacco-producing states are Kentucky and North Carolina. They account for 71% of all tobacco grown in the United States. Tobacco is an addictive substance because it contains the chemical nicotine. Like heroin or cocaine, nicotine changes the way your brain works and causes you to crave more and more nicotine. This addiction to nicotine is what makes it so difficult to quit smoking and other tobacco. Learn more about nicotine addiction.