The Boulder Mountains are a mountain range running roughly north to south located west of Boulder between Helena and Butte in the U.S. state of Montana.

[1] Parts of the range are in four different counties: Deer Lodge, Jefferson, Lewis and Clark, and Silver Bow.

[1] Haystack Mountain, which reaches 8,819 feet (2,688 m), is the tallest peak in the range.

[5] There is a SNOTEL weather station near the summit of Rocker Peak at an elevation of 8,000 ft (2,438 m).

Rocker Peak has a subalpine climate (Köppen Dfc), bordering on an Alpine climate (Köppen ET).