The marathon is a long-distance race, completed by running, walking, or a run/walk strategy. There are also wheelchair divisions. The marathon has an official distance of 42.195 kilometres (26.219 miles; 26 miles 385 yards), usually run as a road race. The event was instituted in commemoration of the fabled run of the Greek soldier Pheidippides, a messenger from the Battle of Marathon to Athens, who reported the victory.
The marathon was one of the original modern Olympic events in 1896, though the distance did not become standardized until 1921. More than 800 marathons are held throughout the world each year, with the vast majority of competitors being recreational athletes as larger marathons can have tens of thousands of participants.
The Boston Marathon began on 19 April 1897, and was inspired by the success of the first marathon competition in the 1896 Summer Olympics. It is the world's oldest run annual marathon, and ranks as one of the world's most prestigious road racing events. Its course runs from Hopkinton in southern Middlesex County, to Copley Square in Boston. Johnny Hayes' victory at the 1908 Summer Olympics also contributed to the early growth of long-distance running and marathoning in the United States. Later that year, races around the holiday season including the Empire City Marathon held on New Year's Day 1909 in Yonkers, New York, marked the early running craze referred to as "marathon mania". Following the 1908 Olympics, the first five amateur marathons in New York City were held on days that held special meanings: Thanksgiving Day, the day after Christmas, New Year's Day, Washington's Birthday, and Lincoln's Birthday.
Overconsumption is the most significant concern associated with water consumption during marathons. Drinking excessive amounts of fluid during a race can lead to dilution of sodium in the blood, a condition called exercise-associated hyponatremia, which may result in vomiting, seizures, coma and even death. Dr. Lewis G. Maharam, medical director for the New York City Marathon, stated in 2005: "There are no reported cases of dehydration causing death in the history of world running, but there are plenty of cases of people dying of hyponatremia.