I believe it predates 1915. Found an article listing in an August 8, 1915 Pawhuska Newspaper that lists "Freeninn's Rexall Drug and Jewelry"... guessing here, but would imagine that is the same one since it sold drugs and jewelry. Pawhuska was a very incorporated city in 1915, with their own Electric Plant and lots of Natural Gas, so in the early 1900's it was the place to be!
From an 1884 Article about the Osage Nation:
"Pawhuska now has five large general merchandise stores, besides sev-
eral smaller ones, doing a good business, four hotels, three banks, three
drug stores, four meat markets, three exclusively groceries, four livery
barns, three blacksmith shops, six restaurants, three barber shops, four
millinery parlors, four lumber yards, three wagon yards, two photograph
galleries, two bakeries, two gents' furnishing stores, two racket, and sev-
eral smaller stores and many roomiing and boarding houses sufficient to
entertain all comers till the lot sale, when the population may double in the
next year."