Mount Jefferson - Montana Mountain Project

Sara heading towards Mount Jefferson

Hidden to the West of Yellowstone National Park is the small Centennial Mountain Range. Although often overlooked because of its proximity to the National Park and the larger Madison mountains not far off, this range offers a quiet experience that isn't too far off the beaten path.

After the Rut Mountain Runs last year we took the long way back to Missoula and drove south to Island Park where we connected with Sawtelle Mountain road, which gives Mount Jefferson relatively easy access for it's 3,380' of prominence. The radio towers on the top of neighboring Sawtelle Mountain require year-round access so the FAA maintains a massive dirt road year-round. From the trailhead near the top of the road we were able to follow the friendly trail along an old logging or mining road (we didn't even realize it was a road bed until the return trip) through stunted fir and a few whitebark pine.

Gotta love trails that start up high!

With tired legs from working and racing the Rut we opted - not that we had a choice on tired legs - for a more casual pace and spent a lot of time looking at the distant Tetons. The relatively small Centennial Mountains form the Continental Divide as well as the boundary between two mighty rivers in this area. To the west are the headwaters of the Snake River and draining the east side of Mount Jefferson is Jefferson Creek, the main tributary to the Missouri River. So although it's a small range the geological significance of this range is great as a divider between important waterways.

The range itself runs East to West in a land where most ranges run North/South. This is more than just a rebellious phase, however, as the Centennials are thought to have been formed by the movement of the Yellowstone Hotspot, which also formed the Island Park Caldera (yes, the one that erupted and swallowed Woody Harrelson in the movie 2012). Ash from this 2.1 million year old eruption has been found as far as St. Louis and Southern California. The range was likely formed as hot magma flowed down the western slope of the caldera; the same slope that would form the Centennials and Mount Jefferson. The mountains in this area are covered with a 1,000' thick layer of block lava and are deeply cut by glaciers. While hiking the CDT in 2014 we hiked up the nearby Hellroaring Canyon and were treated to the leftovers of that glacial retreat.

Looking out over Henry's Lake

After following the trail for a couple miles we veered off and stayed on the ridgeline (apparently the lip of the caldera) as the trail turned North and dropped down into Rock Creek Basin. We quickly climbed above the subalpine fir and continued hiking through what was left of the summer grasses. The slope to our left (Idaho) was steep, but looked friendly while the Montana side fell away sharply down into Rock Creek Basin.

The summit of Mount Jefferson is actually comprised of three different points that wrap around the western edge of the basin in an impressive 1,000' cirque. We reached the highest of the high points first and at 10,203' stood on the top of the Centennials. Luckily we chose a day that afforded us incredible views of the Tetons, Henry's Lake Range, Madisons, the Gravellys, the Beaverheads, and deep into Yellowstone. Not to mention we could see the braids of the Snake River forming and shimmering off in the distance.

Anyone know what the cuts are for in this hillside?

Looking at Point 9584 just to our northeast there appeared to be a series of logging or mining roads cut into the slope that reminded me of ancient irrigation terracing in Arizona or China. I haven't found a satisfactory answer as to what these are so if you have any idea please let me know!

Instead of following our same path back we dropped down into Rock Creek Basin and hiked across the basin bottom until rejoining the trail. This was a pleasant way to go in September, but the myriad of low hollow spots hinted at a boggy swamp in late spring. We would think twice about hiking back this same route during the spring thaw!

On top of Mount Jefferson

After returning to the car we drove the last mile or so to the top of Sawtelle Peak in order to get another view of Mount Jefferson and the mysterious lines in the ground. The different perspective did nothing to help reveal the purpose of the cuts in the mountainside so we got back in the car and drove back to Missoula.

Sara out on the next point of Mount Jefferson with the Continental Divide behind