Marijuana What is marijuana, and how has it effected us all? As we all may, or may not know, marijuana use is on a constant rise in the United States. Marijuana is and has long been the most widely used illegal drug in the United States. It is used here more frequently than all other illegal drugs combined. According to conservative estimates, one third of the American population over the age eleven has smoked marijuana at least once. More than 17 million Americans smoked it in 1992. At least three million smoke it on a daily basis. Unlike heroin or cocaine, which must be imported, anywhere form a quarter to half of the marijuana used in this country is grown here as well. Th