Larry Gassen is a photographer who was invited to shoot photographs of people who had just completed the Western States Endurance 100-mile endurance Run.
It is the most famous 100-mile race in the country, and perhaps the world.
The course features 18,000 feet of elevation gain, and 23,000 feet of elevation loss.
There is a 30-hour time limit. The course record is just over 15½ hours.
View the entire gallery here.