The part of the park we hiked in is called Scull Shoals Experimental Forest. A map of the forest can be found here in PDF form, and the portion we hiked is in the most northern tip. We hiked the trail highlighted pink in the map below. It was approximately 4 miles long.
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The trailhead is circled on the map above where it comes close to Forest Road 1231. It is just north of the intersection with Forest Road 1231D. The sign below, on the west side of 1231, indicates you have found the trailhead.
The trail is lightly used, but is marked the whole way with plastic orange diamond trail blazes, and plastic green diamong trail blazes with an orange horse. On the western portions of the trail, there are many trees down across the trail, and new paths have circle around them. Be careful to find the blazes again!