Where the Marathon Began
The first organized marathon race was held in Athens, the capital of Greece, in 1896. It took place as part of the very first modern Olympic Games. The race was the centerpiece event of those Games, and it has been part of the Olympics ever since.
A Race Rooted in Legend
The marathon was not a random choice for Athens. It was inspired by an ancient Greek legend about a messenger who supposedly ran from the town of Marathon all the way to Athens to deliver news of a military victory, then collapsed from exhaustion. A French organizer of the 1896 Games suggested creating a long-distance race that followed this legendary route, and the idea was enthusiastically embraced. The race ran roughly from Marathon to Athens, finishing in a grand stadium.
A National Hero
The first marathon was won by a Greek runner named Spyridon Louis, and his victory turned him into a national hero overnight. The whole stadium erupted, and members of the Greek royal family reportedly ran alongside him as he approached the finish. The standard marathon distance used today was not yet fixed in 1896 - that exact length was settled at a later Olympic Games.
Source
This article was written using information from Wikipedia.