I didn't have a car. I walked, biked, and took a taxi -- sort of an impromptu triathlon.
I walked to a good history museum on the Capitol Grounds. It has a very cool dinosaur skeleton and many other interesting exhibits. From there, I walked around a golf course, through a university campus, and then over some mountain bike trails that cut down to the Missouri River.
There is a bike rental place by the river in Bismarck. From there, bike trails connect all the way to Ft Lincoln and General Custer's former residence. It is kind of a long way. I took a taxi back to the hotel, which was uphill, after I was done.