The magnificent George S. Mickelson Trail runs 109 miles from Deadwood on the north to Edgemont on the south. Riders will traverse over 100 converted railroad bridges and bike through four rock tunnels. The trail surface is primarily crushed limestone and gravel. There are 15 trailheads, all of which offer parking, self-sale trail pass stations ($3 per rider per day in 2011), vault toilets, and tables. The trail is named for the governor who spearheaded the construction of this marvelous trail.
Most of the trail has a gradient of under 4%, but some segments exceed that and should be considered strenuous. Dumont is the highest section and the longest incline is the 19 mile section from Deadwood to Dumont.
I parked in Hill City along Railroad Avenue and biked 7 miles south, returned, then biked 5 miles north and back. Both directions out of town were consistent uphills, but the rides back to town were speedy coasts downhill.
The scenery around every bend is knockdown gorgeous as these photos attest. Bring plenty of water and bring a camera. Most of my shots are while I was pedaling, but stopping for photo opportunities make for a pleasant rest stop.
The trail is mostly in fine condition, though some sections had indications of vehicular traffic, as one section where logging was occurring. I would not recommend a road bike, but any hybrid or full-mountain bike would work fine.
The trail follows the route of the former Chicago, Burlington and Quincy Railroad and was built in 1890-91. In 1934, the CB&Q ran the famous Pioneer Zephyr, the first diesel powered streamlined passenger train on this route. The CB&Q was obtained by the Burlington Northern in 1970 which operated the right-of-way until 1983.
Trailhead info is here.
Trail map with elevation/contour map (with downloadable PDF)