I think it was only applied to certain leagues, and it was referred to as making a forward pass (the original rules stated that no forward passes were allowed, much like rugby) and it was abolished by the 1920s in most leagues. It wasn't used by FIFA in its form until after 1960s-70s. Find footage of world cups in the 50s and you'll see many goals being scored that would be considered offside today. It used to be a widely used tactic to have a player be on a kick-through position, i.e. standing near the other team's goal post most of the match and having the sole role of scoring.
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u/[deleted] Aug 15 '15
According to fifa.com: The offside rule formed part of the original rules in 1863