It was established in 2006 in order to bring national visibility to ultra-endurance mountain bike racing.
Each of the races is approximately 100 miles (160 km) long and primarily off-road.
The title of series champion is awarded to the racer with the four best results in each of the following categories: Men's Open, Women's Open, Men's Masters (age 50+), and Single speed.
Any ties are broken by the placing results in the final race of the series.
[3] Some of these races were run before joining the NUE series.