What is a US league?
A US league is three miles or 15,840 feet. The word comes from the Late Latin leuca, a Gaulish measure traditionally taken as an hour's walk.
The league was used for the distance between towns and for a ship's run at sea. The mile and the kilometer replaced it, and it now mostly turns up in older books. A US league of three miles is about 4.83km.
What is a UK league?
A UK league was three miles, or about 4.828 kilometers. The length of a league varied between countries and centuries – three miles is the English figure.
The league has long since dropped out of use in Britain and survives mainly in fiction. Seven-league boots, at three miles a league, would cover 21 miles a step.