Thank you, Dan! That almost worked. My .shp files seem to be in different spatial coordinates (one is GSC_North_American_1983, the other is GSC_WGS_1984). I tried a few transformations, but there doesn't appear to be an exact one. As a result, some counties get matched to multiple divisions (I allowed, "one-to-many" match) because their borders spill over a tiny bit. I've tried "one-to-one" matching and that seems to work, but I'm not sure how it chooses which division to match to - would it be the one that matches best (that would be ideal)?