I'm a native South Dakotan, but I like the drive through North Dakota better, more things to see, especially in the western part around Teddy Roosevelt NP. Take the freeway or go on US 2 and make sure you stop at Fort Union where the Yellostone River meets the Missouri. Will make your visit to Livingston more meaningful since that's on the Yellowstone also. Good CG's in the NP and no doubt private or county/municipal CG's along the way. Another must see place is at the Mandan village where Lewis & Clark spent the winter of 1804-05 with the Mandan Indians, probably good camping spots nearby but I'm not sure.