Correction: The purplish-flowered plant is an Elephantopus scaber. I really butchered the name.
Need suggestions for wildflowers for a sunny clearing
Muddy, did you ever get an ID on the "three leaved mystery vine"? I think it may be Amphicarpaea bracteata, commonly known as hog peanut.
http://www.illinoiswildflowers.info/savanna/plants/hog_peanut.html
It is native and found in the eastern and central US and Canada.
I think you're right! It looks just like that. I read that it blooms in August or September, which would explain why I haven't noticed blooms on it yet. I am so excited that it's a native plant. It has covered most of the Japanese stilt grass growing in the same area, although some grass pokes through here and there.
Nice one. Lucky you! :)