Thanks Heather. I looked up the other Joel Canterbury son of Asa and no one has any dates or other information for him, other than that his father was b. 1720. Since Mary Adaline was b. 1818, I'm thinking Asa probably wasn't her grandfather, since it's kind of unusual for a grandparent to be 100 years older than oneself. The census data line up with Mary Adaline being a son of your Isaac Joel, and Mary was reputedly married in Gallia Co., OH where Isaac Joel lived, so I'm inclined to think that's her father. None of the trees I saw online for him account for a daughter born 1815-1820.
I'll let you know if I find out anything more. Thanks for writing back.