The Western States Endurance Run, known commonly as the Western States 100, is a 100.2-mile (161 km) ultramarathon in  California’s Sierra Nevada Mountains trails yearly on the last full weekend of June. The race starts at the base of the Olympic Valley ski resort and finishes in Auburn, California. The terrain is quite rugged, frequently showcasing snow on the highest passes and record hot temperatures throughout the course.  Runners ascend a cumulative total of 18,090 feet (5500 m) and descend a total of 22,970 feet (7000 m) on mountain trails before reaching the finish. Because of the length, the race commences at 5 a.m. and continues through the day and into the night. Runners finishing before the 30-hour time limit for the race receive a commemorative bronze belt buckle, while runners finishing in under 24 hours receive a silver belt buckle.

The Western States 100 is one of the five 100-mile races comprising the Grand Slam of Ultrarunning, including the Old Dominion 100, Vermont 100 Mile Endurance Run, and the Wasatch Front 100 Mile Endurance Run in Utah and the Leadville Trail 100 in Colorado.

The Western States Board of Trustees has instituted rules around the overall lottery and selection process, which you can see here.