I figured to submit this FKT because the Green Rock Trail is a fantastic route and a challenging test piece for ultrarunners in the St. Louis area! Started from the southern TH at Fox Creek Road with 1L of water and 6 gels in my running vest. Got to the northern TH and ran 0.1 miles on the road to refill water from the nearby fountain, then ran back to the trail to continue. Other than a couple confusing intersections, the trail is well marked by white blazes and signs. Felt fatigued starting around mile 25. Did this as a training run in the middle of a 80 mile week, could definitely shave off time if done as a true FKT attempt.
out & back
4h 47m 36s