The league was used in Ancient Rome, defined as 1.5 Roman miles (7,500 Roman feet, 2.2 km, 1.4 mi.). The origin is the "leuga gallica" (also: leuca Gallica), the league of Gaul.

A league is a unit of length (or, in various regions, area). It was long common in Europe and Latin America, but it is no longer an official unit in any nation. The word originally meant the distance a person could walk in an hour. Since the Middle Ages, many values have been specified in several countries.

More Info: en.wikipedia.org