From Natural Chimneys the 100K climbs Narrow Back Mtn, descends to the Wolf Ridge climb, connects to Timber Ridge, crests Sand Spring Mtn and descends Sand Spring Trail, reaches North River Gap and climbs the Wild Oak National Recreation Trail over Lookout and Hankey Mountains, descends Magic Moss to Camp Todd, climbs the Horse Trough Hollow and Little Bald Knob, crosses Chestnut Ridge to Grindstone Mtn and back to North River Gap, then retraces the Tillman Trail back over Narrow Back Mtn to the finish at Natural Chimneys.
A trail ultramarathon run through the George Washington and Jefferson National Forests west of Virginia's Shenandoah Valley, offering 100 Mile, 100K, 50K and 21K distances from a shared start/finish at Natural Chimneys Park. The 100 Mile starts at 6:00 PM Friday and carries a 36-hour cutoff, so every finisher is on the course for two nights. Part of the UTMB World Series since 2023; a dual qualifier for the UTMB World Series Finals in Chamonix and the Western States Endurance Run.
Founded in 2008 by Dr. Clark Zealand as an out-and-back 100-miler starting and finishing at Camp Shenandoah, a Boy Scout of America camp near Swoope, Virginia, climbing Elliott's Knob in both directions. It ran as the fourth race in Virginia's "Beast Series" (Holiday Lake 50k, Terrapin Mountain 50k, Promise Land 50k, Grindstone 100M, Mountain Masochist 50 Mile, Hellgate 100k). The race has started at 6:00 PM Friday since its first year in 2008. In 2023 it joined the UTMB World Series and was rebranded Grindstone Trail Running Festival by UTMB; the start/finish moved from Camp Shenandoah to Natural Chimneys Park & Campground in Mount Solon, Virginia (about 20 miles away, also in Augusta County) to accommodate a larger field, and 100K, 50K and 21K distances were added alongside the original 100 Mile. The night start has continued unchanged through both the rebrand and the venue move. Many third-party listings (Wikipedia, the American Trail Running Association's event database, and other race-aggregator sites) still describe the pre-2023 Camp Shenandoah course and Swoope address as current; they have not been updated for the relocation.
| Mile | Station | Cutoff | Crew | Bag | Pacer | Med | To next |
|---|---|---|---|---|---|---|---|
| 0.00 |
Natural Chimneys - Start
1,342 ft
|
? | ● | ● | ? | ? | 5.70 |
| 5.70 |
Lick Run 1
1,759 ft
|
? | ? | ? | ? | ? | 5.70 |
| 11.40 |
Wolf Ridge
1,814 ft
|
9:00am | ? | ? | ? | ? | 9.60 |
| 21.00 |
Sand Spring
1,936 ft
|
11:45am | ? | ? | ? | ? | 4.20 |
| 25.20 |
North River Gap 1
1,611 ft
|
1:00pm | ● | ● | ? | ? | 5.70 |
| 30.90 |
Lookout Mountain
2,595 ft
|
? | ? | ? | ? | ? | 7.20 |
| 38.10 |
Magic Moss
2,310 ft
|
4:30pm | ? | ? | ? | ? | 5.00 |
| 43.10 |
Camp Todd
2,359 ft
|
6:00pm | ● | ● | ? | ? | 9.70 |
| 52.80 |
North River Gap 2
1,611 ft
|
9:00pm | ● | ● | ? | ? | 7.70 |
| 60.50 |
Lick Run 2
1,759 ft
|
? | ? | ? | ? | ? | 4.50 |
| 65.00 |
Natural Chimneys - Finish
1,342 ft
|
12:00am | ● | ● | ? | ? | ? |
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