Why is a marathon race 26.2 mi long?

Answer 1

The length of a marathon was not fixed at first, since the only important factor was that all athletes competed on the same course. The marathon races in the first few Olympic Games were not of a set length, but were approximately 40 kilometres (25 mi),[12] roughly the distance from Marathon to Athens by the longer, flatter route. The exact length of the Olympic marathon varied depending on the route established for each venue.

The standard distance for the marathon race was set by the International Amateur Athletic Federation (IAAF) in May 1921[13][14] at a distance of 42.195 kilometres (26 miles 385 yards). Rule 240 of their Competition Rules specifies the metric version of this distance.[15] This seemingly arbitrary distance was that adopted for the marathon at the 1908 Summer Olympics in London. At a meeting of the International Olympic Committee in The Hague in May 1907 it was agreed with the British Olympic Association that the 1908 Olympics would include a marathon of about 25 miles or 40 kilometres.[16] In November 1907 a route of about that distance was published in the newspapers, starting at Windsor Castle and finishing at the Olympic Stadium, the Great White City Stadium in Shepherd's Bush in London.[17] There were protests about the final few miles because of tram-lines and cobbles, so the route was revised to cross the rough ground of Wormwood Scrubs. This lengthened the route, as did plans to make the start 700 yards (640 m) from Queen Victoria's statue by Windsor Castle, and it was decided to fix the distance at 26 miles (42 km) to the stadium, plus a lap of the track (586 yards, 2 feet),[17] using the Royal Entrance as the marathon tunnel, and finishing in front of the Royal Box.