Jennifer...I agree that the Taum Sauk section between 21 and A is an awfully nice section.
It is around 33 miles. Easily done in 3 days. If things go well, you can also loop to the top of Bell Mountain, with really nice views to the east. This is just 2 miles before the Hwy A TH.
The hike will take in Mina Sauk Falls, Taum Sauk highpoint, Johnson Shut-Ins (and The Scours). It crosses several of the area "mountains" and there are some very nice rock glade areas to camp in, or streamside campsites if that's preferable...water is plentiful, including a couple springs.
Hopefully, I'll be getting back to the OT shortly, our next section is 32/DD to say, maybe, P or 106...
-Mark in St. Louis