Shanna Ailes-Istnick placed first in the women's race.
It was the fourth consecutive XTERRA National Championship for King.
He was racing the ultra to train for the upcoming world championships.
Approximately 100 runners are expected to take part in the ultra.
Competitor.com’s Sean McKeon took a trip to Mammoth Lakes, Calif. to learn what it’s like to train for a day with American 50K