back + forty, meaning “back side of a farm”. In the Homestead Acts (1860s–), farmers were granted a quarter section; a section was nominally 1 square mile containing 640 acres, a quarter section was 160 acres, and the quarter section was itself subdivided into four quarter-quarter sections of 40 acres each: two front forty and two back forty.
- (US) The remote part of a farm.
- They couldn't contact the farmer right away because he was out plowing the back forty
- (US, idiomatic) The most remote or inaccessible part of any place.
- (remote place): See: Thesaurus:remote place