Based mostly on the singularly born berries, my best guess would be Amelanchier bartramiana, but really, there isn't enough detail in the pics to know.
As a child and through high school, I spent at least a month every summer at our cabin a half mile south of the BWCAW. Most of that time exploring the wild. Olga Lakela's A Flora of Northeastern Minnesota was an indispensable companion.
