Vernon, according to people in the Oklahoma
Native Plant Society group on FB, there are only a couple of counties right hard up against the Arkansas border where pawpaws grow wild in OK. If I could be more specific, I would be -- but people tend to be vague about the locations of their favorite pawpaw patches.
However, with proper care, they are said to be growable throughout much of the state. Fair warning; germination from seed is tricky and/or slow; I've currently got my fingers crossed over seeds from a generous Permies member further east. (I am storing them in peat moss until spring.)
I can report that there is a lovely pawpaw tree in the Cherokee Nation Heirloom Garden in Talequah. I haven't been there to see it in fruit, but it is a large, healthy, on-the-young-side-of-mature tree.