Surrounded on three sides by the meanderings of the Big Hole River [1], the Pioneer Mountains are in fact two different ranges divided down a north-south axis, linked yet separated, sort of like the underside of a coffee bean. These out-of-the-way mountains come to life in the winter; a hot springs resort [2] and a small downhill ski area [3] combine to bring in the locals. In the summer the hills are covered with violet-blue lupine. The Wise River drainage is popular with anglers; there are several large Forest Service campgrounds with fishing access along the river.
Highway 484 bisects the Pioneer Mountains, from Wise River in the north through Polaris to Highway 278 in the south. The Forest Service has designated this route running down the furrow of the coffee bean as the Pioneer Mountains Scenic Byway.
Links:
[1] http://www.moon.com/destinations/montana/butte-helena-and-southwestern-montana/the-big-hole-river-country/the-lower-big-hole-river
[2] http://www.moon.com/destinations/montana/butte-helena-and-southwestern-montana/the-big-hole-river-country/the-pioneer-mounta/elkhorn-hot-spr
[3] http://www.moon.com/destinations/montana/butte-helena-and-southwestern-montana/the-big-hole-river-country/the-pioneer-mounta/maverick-mounta