Many ultras have historical significance, including the Spartathlon, based on the 246 km run of Greek messenger Pheidippides from Athens to Sparta during the Battle of Marathon in a day and a half to seek aid against the Persians.

Timed events are generally run on a track or a short road course, often one mile (1.6 km) or less.

[12] The format of ultramarathons and the courses vary, ranging from single loops (some as short as a 400-metre (1,300 ft) track),[13] to point-to-point road or trail races, to cross-country rogaines.

Usually, there are aid stations, whether every lap of a track, small road or trail loop courses, or extending up to perhaps 20 to 35 kilometres (12 to 22 mi), where runners can replenish food and drink supplies or take a short break.

Concerns have been raised about rising entry fees, homogenization of racing experiences, and bulldozing of smaller events.

[106] Ultrarunning has become popular in Asia, and countries such as Japan, Taiwan, and South Korea have hosted IAU World Championships.

[citation needed] Australia has seen a steep growth in ultrarunning events and participants in recent years.

[121][122] The Australian Ultra Runners Association (AURA) has a comprehensive list and links of events and their respective results.

[127] The other races in the UTMB festival, including the CCC, TDS, and OCC, are also significant events in the ultrarunning calendar.

[128] The oldest existing ultramarathon in North America is the JFK 50 Mile,[129] which began in 1963 as a push by President John F. Kennedy to bring the country back to physical fitness.

[131][129] The first mountain trail ultramarathon held in the United States was the 1911 Mount Baker Race (50K), in Bellingham, Washington.

Runners raced by car or train to the trailheads, ran up and down Mount Baker 10,000 feet, and then returned to the city.

Tomas Zafiro and Leoncio San Miguel, both Tarahumara Indians, ran 100 km from Pachuca to Mexico City in 9 hours and 37 minutes.

[134] In the 1980s, Gary "Lazarus Lake" Cantrell and Karl "Raw Dog" Henn conceived the Barkley Marathons, an annual trail race held in March or April in Frozen Head State Park, Tennessee.

[citation needed] Since 1997, runners have been competing in the Self-Transcendence 3100 Mile Race, which is billed as the longest official footrace in the world.

[135] The current record holder is Ashprihanal Pekka Aalto, at 40 days 09:06:21 for a daily average of 76.776 miles (123.559 km) in 2015.

Candidates for the Hall of Fame are chosen from the 'modern era' of American ultras, beginning with the New York Road Runners Club 30 Mile race held in 1958.

The Inaugural inductees were Ted Corbitt, a former US Olympian, winner of the aforementioned race in 3:04:13, and co-founder of the Road Runners Club of America, and Sandra Kiddy, who began her ultra career at age 42 with a world record at 50 kilometers, 3:36:56, and who went on to set a number of US and world ultra records.