From Bozeman, US 191 is concurrent with I-90 eastward to Big Timber, where it proceeds north. The road travels through hilly ranch country near the eastern edge of the Crazy Mountains to Harlowton, where US 191 is briefly concurrent with US 12. North of Harlowton, US 191 is concurrent with MT 3 for to Eddie's Corner, where US 191 proceeds eastward to Lewistown on a roadway shared with US 87 and MT 200, in a wrong-way concurrency.
