Absaroka Range, Wyoming Whitwater Rivers Boulder River Class III - 4.5 miles long (McLeod to Highway bridge) Sweet Grass County Boulder River Class V+ - 1 miles long (Boulder Falls to Highway) Sweet Grass County Boulder River Class II-III - 9 miles long (Chippy Park Campground to Boulder Falls) Sweet Grass / Park County Boulder River Class III-IV - 5 miles long (Speculator Creek to Chippy Park Campground) Sweet Grass County Boulder River Class III-V - 4 miles long (Fourmile to Speculator Creek) Sweet Grass / Park County Boulder River - East Class I-II - 12 miles long (Headwaters to Boulder River) Sweet Grass County Boulder River - West Class II-III - 14 miles long (Gallatin National Forest boundary to Boulder River) Park Sweet Grass County Clarks Fork Yellowstone Class IV - 3 miles long (Trailhead to State line) Park County Clarks Fork Yellowstone River Class III-V - 4.2 miles long (Upper) Park County Clarks Fork Yellowstone River Class IV-V+ - 2.6 miles long (Honeymoon) Park County Clarks Fork Yellowstone River Class V+ - 22.9 miles long (Box) Park County Clarks Fork Yellowstone River Class III-V - 3 miles long (Lower) Park County Crandall Creek Class III-V - 4 miles long (Trailhead to Clarks Fork Yellowstone Rail Road) Park County Greybull River Class I-III - 6 miles long (Venus Creek to Forest Service boundary) Park County Rock Creek Class II-IV - 10 miles long (Lake Fork to Red Lodge) Carbon County Rosebud Creek - East Class IV-V - 6 miles long (Lake to Sand Dunes Campground) Carbon County Rosebud Creek - West Class III-IV+(V) - 3 miles long (Emerald Lake to Pine Grove Campground) Stillwater County Shoshone River Class II-V - 8.1 miles long (Buffalo Bill Dam to Highway 120) Park County Shoshone River - North Fork Class I-III - 40 miles long (Pahaska Tepee to Buffalo Bill Reservoir) Park County Shoshone River - South Fork Class II-IV - 13 miles long (East Fork Creek to Trailhead) Park County Stillwater River Class I-III - 11.8 miles long (Buffalo Jump to Cliff Swallow) Stillwater County Stillwater River Class I-V - 3.5 miles long (Woodbine Campground to below Chrome Mine) Stillwater County