Located north of Fort Smith and south of Fayetteville. One of the most heavily-used of Arkansas state parks. The Visitor Center is at 35.7802°N, 94.2503°W. April ’12 trip.
Maps
I haven’t mapped the area myself yet but OuachitaMaps.com has one for the Butterfield Trail.
Trails
Butterfield: a 15 mile loop, mostly in the national forest outside the park boundary. No primitive camping within park boundary. Get a free permit at the visitor center.
Yellow Rock: 3 miles. One way or round trip? I don’t know, probably round trip.
Fossil Flats: primarily a mountain bike trail?
Lake:
Devil’s Den: A short trail with much interesting geology.
Lee Creek:
Last review/update:
The Compulsive Hiker 