Convert from city block [Midwest U.S.] to league [UK]

Unit Definition (city block [Midwest U.S.])
The city block is an informal unit of distance popular in the U.S. A block is the average distance between street intersections in the rectangular street grids common in most American cities. The length of a block varies from about 1/20 mile (80 meters) in New York to about 1/16 mile (100 meters) in many midwestern cities to about 1/10 mile (160 meters) in cities of the South and West. (In New York and some other cities, streets running on one direction are closer together than streets running perpendicular. In these cities, people often speak of "short blocks" or "long blocks.")

Unit Definition (league [UK])
The league became a common unit of measurement throughout western Europe, although its length varied greatly from region to region. It was originally intended to represent the distance a person could walk in an hour. In many cases it was equal to 3 miles, (note that the definition of a mile also varied from region to region). At sea, the league was often equal to 3 nautical miles, which is 1/20 degree or 5556 meters (metres). In the USA and Great Britain, the league is defined to be 3 statute miles on land, or 3 nautical miles at sea.