The routes are on top of Sentinel Butte, not in the town. Sandstone rock that is brittle. Bolted in 2003 with expansion bolts and should be inspected before use. The land is privately owned, but the owner doesn't mind. Don't leave a mess! Somewhat of a tourist attraction
Take Interstate 94 west from Bismarck, past Dickinson to Exit 10. Go south into the town of Sentinel Butte. Go straight through Sentinel Butte for two miles to a Y and go right (SW) Follow that road up to the top of the butte. Drive towards the back and stop as the road turns left. Routes are NE of here. Ask some locals for directions if need be.
I have some photos of the area and I will post them. I was at Sentinel Butte today. The anchors are 13 mm bolts with extremely large hooks. There use to be a rappel route but the anchors were missing and only the bolts remain. The route is 5 anchors and maybe 40 meters.