The marathon is 26 miles and 385 yards long (26.2 miles), which is equal to 42.195 kilometers. This length was established as the standard for marathon races in 1921 by the International Amateur Athletic Federation. Prior to that, the length of the race varied depending on the route established for each venue.
The marathon race is this particular length in honor of the run made by a soldier named Pheidippides at the Battle of Marathon of 490 B.C., when the heavily outnumbered Athenian army defeated the invading Persian army at Marathon. According to legend, at the conclusion of the battle, Pheidippides ran from the battlefield all the way back to Athens to bring word of the victory, a run of approximately 25 miles.