Just for people's information: Originally, there were no hash marks at all on either an American or a Canadian football field. Please, remember that the American Football code developed from Rugby Union Football. Hence, the "Canadian Rugby Football" Union until it became the "Canadian Football League" the 1950's. In Rugby, the ball is always live anywhere on the field until play is called dead (for a penalty; for a scrum-down; etc.). In AF, the ball became "dead" wherever the player in possession was tackled on the field; then, the ball had to be put back into play -- become "live" again -- by scrimmage AT THE SPOT where the ball became dead. If the ball carrier ran out of bounds, then the ball was brought in between 5-15 feet and placed down for scrimmage. There were no hash marks: If a player were tackled near the sideline, then scrimmage occurred at or near the sideline -- which was why all those teams in the "Old, Old Days" had sideline plays in their playbook.
Another related point: AF's Rugby roots also explain why in the Old, Old Days a player had to be TACKLED and HELD DOWN before he was ruled "down." There was none of this: "Did-any-part-of-the-defender's-jersey-brush-across-the ball-carrier's-butt-while-his-knee-was-down?" nonsense? If a ball carrier broke loose, regardless of whether his knee or whole body touched the field, he could still get up an continue running (as in Rugby).
And, another: The ball had to be heeled back in scrimmage. Americans went to the hand-snap pretty early, while Canadians kept it for much longer (e.g., the 1920's). I saw a big picture at the Canadian Football Hall of Fame once -- it was the late 1990's, so I don't know if it's still displayed -- showing (using the American terms) the Center with the Guards bound onto him like a mini-scrum, so that the Center could heel back the ball.
One of the great tragedies of American Football History: Many of the Rugby-esque rules had been maintained by the Canadians, until they started hiring American coaches (i.e., Frank Shaughnessy of Notre Dame), who didn't understand them . . . so, they got rid of them; or, made them like the American game.