Slumgullion Pass (el. 11,530 ft.) is a mountain pass in Colorado traversed by State Highway 149. The north side has the steepest grade of any continuously paved road in Colorado (9%), but the pass does not close often in winter, since snowplows clear the route regularly during this season. It has a few switchbacks and tight spots, but other than that, most travelers will find it an easy, scenic route.
Slumgullion Pass is named for the nearby Slumgullion Slide or Earthflow, a gigantic landslide whose yellowish soil reminded early settlers and miners of slumgullion stew.
The Slumgullion Slide began about 700 years ago when weak volcanic tuff and breccia on the southern flank of Mesa Seco slumped several miles down the steep mountainside. Approximately 300 years ago, a second earthflow started from the top of the mountain and is still active, moving as much as twenty feet per year. Trees growing on the newer slide are tipped at odd angles.
The first flow was so large and cataclysmic, it blocked the Lake Fork of the Gunnison River and created Lake San Cristobal, Colorado's second largest natural lake.