There are many factors that help some states produce more record book bucks than others. I don't know all the particulars of the South Dakota whitetail population, but my understanding is that the rifle season is held during the peak of the rut. This factor would, in my opinion, have more impact on how many trophy bucks exist. Whitetails need age to grow big racks, and when states hold firearms seasons when bucks are most vulnerable, the majority get shot before their second birthday. I know this, because I live in such a state!