Why did they add 300 extra yards onto the 26 mile marathon?

Answer 1

The length of a marathon was not fixed in 1908. When London was awarded the games, the race was advertised as about 25 miles or 40 kilometres. When it was decided to start the race near Windsor Castle, and run past Eton and Harrow (famous public schools), it was obvious that it would be more like 26 miles. Mile markers from the start were cemented in place before the stadium was finished, so although the course of the race was known, its exact distance wasn't. In the end it turned out to be 26 miles 385 yards, or 42.195 metres. The next two Olympics used different distances, but the London one became standard during a meeting of the IAAF in 1921.

Answer 2

The history of the marathon distance dates back to the 1908 London Olympics. When the event organizers were laying out the Olympic course, they had first intended it to be 26 miles, starting at Windsor Castle, and finishing in the white City Stadium, in London.

However, it was decided that the finish line should be in front of the royal box. This determined the distance of 26.2 miles. This marathon distance was officially adopted by Olympic officials in 1924.