A private vehicle is far and away the best means of exploring southwest Montana, as it allows you to appreciate the grandeur of the area. Wide-open terrain affords startling vistas of mountains and prairies, where you're likely to see abundant wildlife. I-90 is the major east-west artery through the region; I-15 is the major north-south route. Most of the other routes here are paved and in good shape, but be prepared for gravel and dirt roads the farther off the beaten path you go. Driving through the mountains in winter can be challenging; a four-wheel-drive vehicle, available from most car-rental agencies, is best.