The Pioneer Mountains cover 2,000 square miles (5,200 km2) in Beaverhead County in southwestern Montana, USA.

[2] Mountain goats inhabit the high crags of the range, while pronghorn utilize the lower elevation grassland foothills.

All told, about 239,000 acres (97,000 ha) of the West Pioneers were roadless as of 1992, including the Wilderness Study Area.

[3] Lakes in the West Pioneers contain perhaps the last pure strain population of Arctic grayling south of Canada.

[3] Wildlife in the West Pioneers includes elk, black bear, moose, pine marten, wolverine, and northern goshawk.