My husband and I are taking a road trip east through Montana this summer, to the northeastern corner to Wolf Point. According to Wikipedia, it's a small city on the Fort Peck Indian Reservation, in the wide, shallow valley of the Missouri River, just below its confluence with Wolf Creek. That bare-bones description is enough to conjure, for me, the allure of the state that has produced some of the finest American writing. William Kittredge and Annick Smith's massive anthology The Last Best Place (University of Washington Press)--its title proclaiming the area's appeal--is a good introduction to Big Sky literature.
I read about Montana long before I visited the first time (when my friend Julie explained "bear bells," then tried to convince me they'd never be needed). First were the brilliant novel Winter in the Blood (Penguin Classics) and the elegant poetry of Riding the Earthboy 40 (Penguin Poets), both by the late James Welch, a founder of the Native American Renaissance. Then came A River Runs Through It and Other Stories (University of Chicago Press) from the "haunted by waters" Norman Maclean, with his famous opening: "In our family, there was no clear line between religion and fly fishing." The iconic memoir by Ivan Doig, This House of Sky: Landscapes of a Western Mind (Mariner Books), was required reading, and led me to his fine fiction--his posthumous novel, Last Bus to Wisdom, is a treasure (as was Ivan). 
Then there's James Crumley's crazy detective story, The Last Good Kiss (Vintage Crime), with another excellent opening line: "When I finally caught up with Abraham Trahearne, he was drinking beer with an alcoholic bulldog named Fireball Roberts in a ramshackle joint just outside Sonoma, California, drinking the heart right out of a fine spring afternoon." And there's Rick Bass, Larry Watson (As Good As Gone), A.B. Guthrie, Jr., Mary Clearman Blew, Pete Fromm, Richard Hugo, Deirdre McNamer... such a clear sense of place. --Marilyn Dahl, editor, Shelf Awareness for Readers