A square mile has 640 acres, and a square parcel of land ¼ mile wide has 40 acres.
An acre is also the area of land that is one furlong (220 yards) long and one chain (22 yards) wide.
It was selected as approximately the amount of land tillable by one man behind an ox in one day. Statutory values were enacted in England by acts of Edward I, Edward III, Henry VIII, and George IV; the British "Weights and Measures Act" of 1878 defined it as containing 4840 square yards.
Acre is the Crusader name given to the city in Israel called Akko in Hebrew, "Akka" in Arabic.
Acre is the name of one of the states of Brazil, see Acre (state)