Legislation concerning the legal minimum drinking age in the United States can be traced back to the days of Prohibition. In 1920, the 18th amendment to the U.S. Constitution declared it illegal to manufacture, transport, or sell intoxicating liquors. This was repealed with the passing of the 21st Amendment in 1933, which was followed by the adoption of minimum legal drinking age policies in all states, with most states electing a minimum legal drinking age (MLDA) of 21. Between 1970 and 1975, 29 states lowered the MLDA from 21 to 18, 19, or 20. This was primarily due to the passing of the 26th Amendment, which lowered the required voting age from 21 to 18.