The Boston Marathon, one of six World Marathon Majors, is a 26.2-mile (42.2 km) race which has been held in the Greater Boston area in Massachusetts since 1897, making it the oldest annual marathon in the world.
The event is held on Patriots' Day, which was April 19 (or April 20 if April 19 was a Sunday) until the implementation of the Uniform Monday Holiday Act in 1971. Since 1971, except in 2020 (race not held) or 2021 (Columbus Day holiday), the Boston Marathon is held on the third Monday in April. Various factors meant that until 1957 the course varied in length, due to which the marathon recognizes several course records that are slower than previous records due to being run on longer courses.