What is significant about the distance 26.2 miles?

According to legend a Greek messenger named Philippides or Pheidippides (there are also other options) ran from Marathon to Athens, without stopping to rest, to announce that the Persians had been defeated and that the Greeks had won. After which he collapsed and died. The run was celebrated by being incorporated into the Olympics and, more recently, into many city runs. The distance from Marathon to Athens was supposedly 26.2 miles.