A league generally represents a distance of about 3 miles, but this can vary because the original understanding of the word referred to the distance someone or something could travel in an hour. While a person walking over land can averages a pace of 3 miles per hour, a boat would travel a greater distance. The term has also represented various lengths in different cultures throughout history.
For the Romans, a league was 1.5 Roman miles, which equates to just less than that in English units, 1.4 miles. A Spanish league is equal to 2.6 miles, but the measurement was put out of use in 1568.