The Centennial Trail, trail mark #89, is a 111-mile trail that runs from just south of Bear Butte in the Northern Hills  to Wind Cave National Park  in the south. Almost 22 miles of the trail runs through Custer State Park . There are three trailheads in the park providing access to the trail. The trail is marked by brown fiberglass posts and gray diamonds. The trail enters the park in the northwest corner of the main section of the park off of Route 87 and ends near the spot where Route 87 enters Wind Cave National Park.
The Iron Creek to Badger Hole Trailhead on the north end of the Centennial Trail is located north of Route 87 on gravel road CSP #345. This segment of the trail is 7.3 miles long and is rated as difficult. The trail ends near a historic cabin (once lived in by Badger Clark, South Dakota’s first poet laureate) just south of Legion Lake.
The trail rises and falls with the gently rolling hills of the area. There are several small stream crossing. About six miles into the ride, the trail climbs steeply and enters an area that was burned in the 1988 Galena fire, a lightning strike fire that burned over 17,000 acres of park land.
The trail continues on to the Badger Hole, the nickname for the cabin once occupied by Badger Clark.
The second trailhead to the Centennial Trail, the Badger Hole Trailhead is located here. The distance between the Badger Hole Trailhead and the final trailhead at French Creek is only 4.2 miles, but it is the most difficult segment of the Centennial Trail in Custer State Park . This trailhead is located one mile off of Route 16A on CSP Road #9, near Legion lake.
The trail winds near CSP Road #9 for about a mile and then heads south and begins to climb up a steep rocky hill. The entire park can be seen from the summit. The trail descends into the French Creek Natural Area. The trail is very steep and rocky as it descends and can be very muddy at the bottom.
The trail follows French Creek, crossing the creek several times and ends at the French Creek Trailhead. This trailhead is located three miles from the Bluebell Stables  on CSP #4. The segment is 10.3 miles long and is moderately difficult. This section of the trail crosses the Wildlife Loop  and enters the open grasslands regions of the park. Pronghorn and prairie dogs will be frequent companions.
There are large herds of bison in this region, so be sure to keep a good distance. Bison are especially protective in the spring when the calves are born and aggressive in late August when the rut season begins. You cannot outride them.
The trail will pass through a gate and then ends at the border of Wind Cave National Park , where bike riding is prohibited.