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23rd September 2023


Offering 11,000’ of vertical gain, adventure awaits as you experience some of the most scenic and challenging sections of the 100-mile course in this 100K version of Grindstone by UTMB.

Race Category


Running Stones



99.7 KM

Elevation Gain

3352 M+

Start Location

Natural Chimneys Park, VA

Start Time




Course Description

Course Description

Starting at the historic Natural Chimneys, the 100k course gets you warmed up before tackling a short but steep climb in order to run along the single-track spine of Narrow Back Mtn. Once down the other side you face the monster Wolf Ridge climb where you connect to Timber Ridge turning left and staying left as you crest Sand Spring Mtn and descend on Sand Spring Trail. Take the Tillman forest access to North River Gap and jump on the iconic Wild Oak National Recreation Trail to climb Lookout Mtn and Hankey Mtn before descending the old-school flow of Magic Moss. Follow the North River forest access to Camp Todd where you rejoin the Wild Oak Trail climbing the infamous Horse Trough Hollow, up and over Little Bald Knob, across Chestnut Ridge to Grindstone Mtn and back to North River Gap. Retrace the Tillman forest access to pick up the Tillman Trail climbing back over Narrow back Mtn to Lick Run before exiting the forest at Bear Trap and cruising your way back to the finish in front of the Natural Chimneys.

Mandatory Gear

  • Minimum water supply: 1 liter of hydration capacity
  • Reusable cup/flask/bottle
  • One (1) working headlamp with spare cells/batteries.
  • Recommendation of 200 lumens or more for night running.
  • Jacket with hood for bad weather in the mountains/course terrain.

Recommended Gear

  • Running pack to carry recommended gear throughout the race.
  • Mobile/Cell phone with international roaming that works in the United States of America.
  • Additional working headlamp
  • Hat

Cut Off Time

9/24/2023 12:00 AM - 18 Hours