The 18th Amendment, also called Prohibition, was a amendment in the United States Constitution. It is the only amendment to be completely reversed.
Section 1. After one year from the ratification of this article the manufacture, sale, or transportation of intoxicating liquors within, the importation thereof into, or the exportation thereof from the United States and all territory subject to the jurisdiction thereof for beverage purposes is hereby prohibited.
Section 2. The Congress and the several States shall have concurrent power to enforce this article by appropriate legislation.
Section 3. This article shall be inoperative unless it shall have been ratified as an amendment to the Constitution by the legislatures of the several States, as provided in the Constitution, within seven years from the date of the submission hereof to the States by the Congress.
The 18th Amendment did not get rid of alcohol. It merely led to a black market. It is similar how today, most recreational drugs are banned, but this only led to a black market. It led to organized crime. In 1933, the 18th Amendment was completely repealed by the 21st Amendment. In modern times, if we end the War on drugs, we could see an end to much of the violence in Mexico, allow for the government to tax drugs, and make better quality drugs available.
There could also be more drug addiction and bigger drug problems generally. There is a stronger case for legalising the softer types of Cannabis than there is for legalising hard drugs.