My first impression is Calico aster, Symphyotrichum lateriflorum.

http://plants.usda.gov/core/profile?symbol=Syla4

Molanic, those lower, cordate leaves suggest that you're in the right group, but Symphyotrichum sagittifolium is now listed as S. cordifolium. It's tough to ID asters from photos. If the upper stems are sparsely hirtellus or pilose, then it might be S. cordifolium (in your area). If the upper stems are densely hirtellus to hirsute, then consider S. drummondii (also in your area). The other eastern US asters in that group are listed in the following excerpt from Alan Weakley's key. Note that Alan recently told me that pasting his information into posts is okay, as long as credit is given. If you have problems reading the text, just click on it for a larger version.

Thank you both for the help. It is good to know that I wasn't totally off base. I'm not knowledgeable enough on botanical terminology to follow keys very well, unfortunately. At the Illinois wildflower site linked below it said this, "In Illinois, the Blue Wood Aster (Symphyotrichum cordifolium) often hybridizes with Arrow-Leaved Aster (Symphyotrichum sagittifolium) and Drummond's Aster (Symphyotrichum drummondii), which can make the identification of some field specimens from this aster complex very difficult".

http://www.illinoiswildflowers.info/woodland/plants/arrow_aster.htm

But it seems like it is most likely in this complex at least, correct?

I've used that site many times for information, because it provides excellent descriptions and good photos. Yes, that does seem like the right group of asters to me.