3 Mile Limit, 12 Mile Limit

When Prohibition went into effect, part of what the US government wanted to establish was how far off the coast they were going to enforce the law. During the 18th century, it was established that 3 miles was the distance a cannonball could be shot from the shore to repel an attacking force. So 3 miles became the de facto extension for enforcing US law, including, centuries later, Prohibition.

Predictably, people began to go just over 3 miles offshore to enjoy a cocktail away from the US authorities. And when the US got other countries, like the UK and France, to agree they could pursue smugglers and drinkers up to 12 miles offshore, well people just moved the party a bit further out.

As a result, the Three Mile Limit and Twelve Mile Limit were created.