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. Parts of the range are in four different counties: Deer Lodge, Jefferson, Lewis and Clark, and Silver Bow.
Haystack Mountain, which reaches , is the tallest peak in the range. The three other highest peaks are Jack Mountain at , Bull Mountain at , and Thunderbolt Mountain at . All four peaks are in Jefferson County.
Rocker Peak, , is near Jack Mountain (Montana), the second highest peak in the Boulder Mountains. There is a SNOTEL weather station near the summit of Rocker Peak at an elevation of . Rocker Peak has a subalpine climate (Köppen Dfc), bordering on an Alpine climate (Köppen ET).