When the 18th Amendment took effect in 1920, the United States officially banned the manufacture and sale of alcohol. Instead of eliminating drinking, Prohibition created an enormous black market almost overnight. Organized crime groups quickly stepped in to supply illegal liquor through bootlegging, speakeasies, and smuggling operations from Canada and the Caribbean. The vast profits generated during these years allowed mobsters to expand their influence, corrupt public officials, and build the criminal empires that would dominate American underworld history for decades.