As a unit of area – In the US, 1 township is 36 square miles (6 miles by 6 miles). Each square mile is divided into 16 subdivisions of 40 acres (1/4 mile by 1/4 mile). Americanisms: "Back forty", "Forty acres and a mule".
General use of the term – The term back forty is used through the northern and western areas of the US to mean a large, remote, often barren stretch of land. The term takes on a figurative cast when, for instance, lumberjacks in New England use it to refer to an out-of-the-way place. And if someone is wasting your time, a Michigander might say, “He’s been plowing the back forty.”
Here at Back Forty Gear, LLC the term back forty describes
any place, near or far, large or small, where we go to enjoy the
outdoors.