With a lot of help from David Polakoff here on the board, I have been able to contact who appears to be one of only two living relatives of Howe McCormick.
Don McCormick now lives in Ocala, Florida, about 35 mile south of Gainesville. The church founded by his great-grandfather (Howe's grandfather) is still very closely tied to the McCormick family, and it was through the church I was able to contact Don.
There wasn't a whole lot of information that he could share with me, as it sounds like the family did not remain close as time passed. But the funny thing was, Don mentioned he hadn't thought of Howe in about ten years, since the church gave him a box of old photos, none of which were labeled except for three. All three either of Howe, Howe and his sisters, or the interior of the store that Howe's father and uncle owned, which is still my bet as to where all the cards came from. Then a week ago, he gets an email passed on to him from the church asking for information of about all things, Howe and his family.
Don has been kind enough to forward scans of those three photos on to me, which I am attaching to this message. He was able to give me a little bit more information on Howe's daughter, who he hasn't seen or heard from since 1981, which might be able to lead me to any other contacts.
It was great to finally find someone who knew Howe, had spoken to him or even really knew anything about him. Don had no idea of Howe's card collection, or the sheer volume of it, and told me that he would now have his radar up for finding any that might still be in the area at antique stores or flea markets (Don collects antique post cards, so he runs somewhat in the same circles). We agreed to stay in touch either by email or phone. His wife Kathryn, who answered the phone, also seemed very sweet.
Howe and his sisters
Howe (guess of around age 6)
The interior of the store owned by William J. McCormick and Alex Howe (Howe's father and uncle (mother's brother)). The gentleman at the far right is Alex Howe. The other two are store clerks, whose name appear on the back of the photo.
Again, thanks to everyone on the board for help in reassembling the collection.