Rock Mountain is a 6,840-foot summit in the central Washington Cascades, north of U.S. Highway 2 between Stevens Pass and Lake Wenatchee, within the Okanogan–Wenatchee National Forest. On Nason Ridge it is second only to Mount Howard. Albert Hale Sylvester, a surveyor and forest official, named the peak. Its slopes drain into tributaries of the Wenatchee River. The mountain stands in the North Cascades, where terrane formation, later volcanic activity, and repeated Pleistocene glaciations shaped steep ridges and ice-carved valleys. East of the Cascade crest, Rock Mountain is somewhat drier than western peaks, though Pacific storms still bring heavy winter snow.