Thanks to a little family ingenuity, Tom's cousin and his wife have steered us in the right direction! After a little online research, we believe our pretty purple-flowered vine to be a wild Purple Rock Clematis (clematis verticillari). I hope you see one next time you're in the woods!
But, bring your bug dope if you're heading north. The mosquitoes are FEROCIOUS, and I have no idea how so many have gotten in the house! My mosquito killing skills have really weakened since last fall . . . .