Henry, I hunted up there a couple of years ago, along the southern shores of lake Sakakawea. The deer stayed in the "coolees" along the river during the day, and came out into the open early and late. We had access to a corn field, rare in those parts, and a number of deer were using it. We even saw an elk one morning, a 5 point bull.
We saw good bucks nearly every hunt, and my buddies missed a few. For us Southern woods hunters, it's really hard to judge distance in the grassland, with deer larger than we are accustomed to seeing. Everybody shot under. We had a blast, but didn't bring home the venison. We saw more whitetails than mulies.