A league is an old unit of length. It was first an ancient Celtic unit. It was the distance a person could walk in about one hour. The Romans adopted the league and it became a common unit of measurement throughout western Europe and Latin America.
In English-speaking countries the league was usually three statute miles (4.828032 kilometres) on land or three nautical miles (5.556 km) at sea. However, in writing the word league often means the Spanish, Portuguese or French league.
The league was used by Ancient Rome, which defined it as being 1 1⁄2 Roman miles (7500 Roman feet or 2.22 km). The origin is the "leuga gallica" (also: leuca Gallica), the league of Gaul. The ancient league was short but the unit grew longer over time.
In Argentina a league is a distance of 5 km.
In Brazil the league was 6 km but it is not used anymore.
The French league had different values at different times: 10 000, 12 000, 13 200 and 14 400 French feet, about 3.25 km to about 4.68 km. It was used for a while together with the metric system but it is not used now. The French league was three nautical miles.
In the Mexican countryside the league is still commonly used in the original sense of the distance a person can walk in an hour. So a league along a good road on level ground is longer than a league on a difficult path over rough ground.
The Spanish league was originally set as a fixed unit of distance of 5,000 varas (a Spanish yard), about 2.6 miles or 4.2 km. In 1568 Philip II of Spain officially abolished the league. However, in parts of Latin America, people still use it (with different meanings in different countries).