American football introduced numbers in 1915 and names in 1961, but in 1967, numbers began indicating a player’s position and eligibility.
Quarterbacks and kickers wear 1 to 19, running and defensive backs 20 to 49, centers and linebackers 50 to 59, guards 60 to 69, tackles 70 to 79, and finally ends and defensive linemen wear between 60 and 89.
And that’s how you tell a football player’s position by his number.
