Bill from Springfield, IL on 8/8/2023 9:07:08 AM:
I'm assuming you've seen the elevation map (link here: https://gfp.sd.gov/userdocs/mickelson-trail-map.pdf) that gives a pretty good description of the entire 109 miles. The first 5.9 miles out of Deadwood are probably the most difficult. After that it's mostly downhill into Hill City (approximate mid-point of the trail).
You'll have a slight climb out of Hill City for about 4 miles and then it's mostly downhill (or flat) all the way to Edgemont.
Since this is a former railroad line, the steepest gradient can't be more than 4% -somewhat like riding into a moderate wind. Of course, those climbing miles are offset by downhills on the other side.
Again, the link to the elevation map I included might be of help, if you haven't already seen it. Enjoy the ride.