Helena [1] and Butte [2] are both served by major airlines. Greyhound travels along I-90, linking Butte [2] to Seattle and Chicago. Rimrock Stage runs the I-15 route, linking Great Falls and Helena [1] to Greyhound at Butte [2].
Driving the local roads can be hazardous in winter; call 406/494-3666 for local road conditions. On the Internet, check www.mdt.mt.gov/travinfo [3].
Links:
[1] http://www.moon.com/destinations/montana/butte-helena-and-southwestern-montana/helena
[2] http://www.moon.com/destinations/montana/butte-helena-and-southwestern-montana/butte
[3] http://www.mdt.mt.gov/travinfo