Through the 18th Amendment to the US constitution, alcohol prohibition was ratified on January 16, 1919 and went into effect exactly one year later through the Volstead Act. Nearly 13 years later, prohibition was repealed by the ratification of the 21st Amendment. The only State to specifically reject the 18th Amendment was Rhode Island.
After Prohibition went into effect it became illegal to produce, distribute or sell
alcoholic beverages. However, it was never made illegal to purchase, possess or consume
those same alcoholic beverages. There were a few exceptions, such as alcohol for religious or medicinal use. The most obvious effect was that illegal businesses that paid no taxes replaced legitimate ones that did.
And so organized crime went 'mainstream', filling a demand made illicit by government prohibition, and a gang of cutthroats and murderers moved into the void left behind by the closing of bars, saloons and liquor stores. "All I do is to supply a public demand … somebody had to throw some liquor on that thirst. Why not me?" Chicago gangster Al Capone. Stellar days for a man of his special 'talents'.
The problems caused by Prohibition continued to increase over time. They threatened the health, safety, morality, economy and well-being of the country. Opposition grew as the problems caused by Prohibition became more and more insidiously.
Here's a good resource on the big 'prohibition' picture:https://www.alcoholproblemsandsolutions.org/18th-amendment/
As for the resulting organized crime syndicates, this sums it up pretty well:https://www.alcoholproblemsandsolutions.org/18th-amendment/
"Alphonse Capone … and a host of other gangsters and 'racketeers', who first came into prominence as the distrubuters of liquor concessions, found that with such weapons as bombs, sawed-off shotguns, machine-guns, and the threat of being 'taken for a ride', they need not confine themselves to the 'beer racket' and the distribution of beer privileges".
It's a real shame that US politicians did not learn from the mistakes of the alcohol prohibition era and resolve to never make that mistake again:
On 17 July 1971, President Richard Nixon declared drug abuse to be "public enemy number one", and once again the cutthroats and murderers were open for business. That was 46 years ago and still no end in sight.