Fortine Creek, a tributary of the Tobacco River, originates on the east slopes of the Salish Mountains in Montana's far northwest corner, just below the U.S. - Canadian border. The creek flows approximately 31 miles north and west to its confluence with Graves Creek, 10 miles east of Eureka, Montana. It runs mainly through timberland, with ranch and farm lands comprising large portions of the lower drainage. Fortine Creek serves as a spawning tributary for Lake Koocanusa cutthroat and rainbow trout.