Picked up mention of this book on another site; have not read it myself.
Nevada Barr, a former Park ranger, has produced a series of books set in national parks and featuring Anna Pigeon as a ranger.
Blood Lure (2002) is set in Glacier NP.
I have not read any of the series (so won't be able to give away the plot, LOL). Potential readers might want to check the reviews on Amazon.
Apparently some of the interest in the series is the main character's development across the books.
Now might also be a good time to read some of the early accounts by or about the Salish and Blackfeet, before GttSR and rangers and reservations and passes and such superstructure ever entered the picture.