Marijuana s the world's most commonly cultivated, trafficked, and used illicit drug, and as the push for legalization at home and abroad grows, marijuana is garnering significant attention from investors, manufacturers, and researchers. Despite the plant being illegal under federal law as a Schedule I drug, the U.S. legal marijuana industry was estimated at $10.4 billion in 2018 with 250,000 jobs devoted to the handling of plants, according to New Frontier Data.