The official marathon distance of 26.2 miles was set to accommodate the British Royal Family during the 1908 London Olympics.

The modern marathon distance is a result of specific logistical requests made during the 1908 London Olympic Games. Before this event, marathon distances were inconsistent, usually measuring around 24 to 25 miles based on the local geography of the host city. The 1896 Olympic marathon in Athens, for example, was approximately 40 kilometers or 24.8 miles.For the 1908 London Games, organizers originally planned a 25-mile route starting at Windsor Castle. However, the Royal Family requested that the race begin on the lawn of Windsor Castle so the royal children could watch from the nursery. To ensure the race ended exactly in front of King Edward VII's royal box at White City Stadium, the course had to be extended to its now-famous length.The final measurement was recorded as 26 miles and 385 yards, which equals 42.195 kilometers. Despite this specific measurement being used in 1908, it was not immediately the universal standard for all races. Other marathons continued to use varying distances for several years following the London Games.The International Amateur Athletic Federation (IAAF) finally stepped in to standardize the event in 1921. They officially cited the 1908 London route as the definitive distance for all future Olympic marathons and international competitions. Today, this 'royal' distance remains the grueling benchmark for runners across the globe.