The origin of the marathon begins in 490 BC, when the king of Persia sent a fleet of 25,000 soldiers to punish the Athenians for revolting. The troops landed in the coastal town of Marathon, where they were met by 10,000 armed Athenians.
The Athenians successfully battled the Persians in Marathon, but some of Persian soldiers set sail for Athens. The Athenians sent a runner (in some accounts a professional runner named Pheidippides) back to Athens to warn of the attack.
On August 12th, 490 BC the messenger ran the 42 kilometre distance without stopping. He would have been subjected to temperatures as high as 39 degrees celcius and just after he arrived in Athens with the news, he died (likely from heat stroke).
What we now know as the marathon commemorates the heroic run from Marathon to Athens。