Backpack the Aero Lakes to Granite Peak

Park County, Montana



26 miles

Elevation Gain

6200 ft

Route Type



Added by Justin Appleby

This truly epic backpacking trip will take you from an abandoned mining camp through rolling forests, across streams, around alpine lakes, through true wilderness, and up steep couloirs to the state of Montana's highest point.  Prepare for some class 4 scrambling.

Granite Peak is considered one of the most difficult state high-points, for its remoteness and its climbing challenge.  Unfortunately, the access to this route is very remote.  Fortunately, this route to the summer is the easiest way up in terms of the technical climbing challenge.  This route, known as the southwest ramp, is the only way up by which rope is recommended as opposed to mandatory.  You will follow about 8 miles of trail and then switch over to class 2 and low class 3 rock-hopping for another 4-5 miles, with the last three-quarters of a mile a true class 4 scramble up to the summit.  Depending on your pace, the trip is doable in one day if you leave in the wee hours of the morning, definitely doable in two days (an afternoon and another full day), or in a two-night trip (the way I'll describe here). 

As you read, use my route data for reference, and strongly consider planning this trip ahead with a GPS device of some kind.  You'll have to forgive me for starting my GPS tracker about a half-mile late, and my watch for dying with about 5 miles left to the car.

Getting There:

From the northeast gate of Yellowstone National Park, take US-212 East for almost 6 miles, and then turn left (North) onto Lulu Pass Trail Road.  Your roads from here on our will be dirt, 4WD, high clearance recommended, and get worse as you near the trailhead.  Follow Lulu Pass Trail Road for 1.1 miles and turn right on the intersecting unnamed dirt road.  Over the next 1.3 miles, there are three dirt roads that fork with this one, but the main one (the one you want to take) is obvious.  Stick with the google maps directions linked above if you are unsure.  After you cross a bridge for Fisher Creek (some small respite to the bumpy roads), you will turn right and uphill onto a narrow dirt road, and this is where the driving gets nasty.  From here it is 0.3 miles to the trailhead, and this is where it would be really handy to have a high-clearance vehicle.  You'll see why.  The trailhead has space for about five cars, and is made obvious by the termination of the road, an abandoned and rusty car, and an abandoned cabin.  Downhill to the right are some cool ruins of an old mining camp.  Coordinates to the parking area are (45.050529, -109.910045).

Reaching Camp

Head around the left side of the old cabin, cross a small creek and meet up with the obvious trail on the other side of some tall grass.  Follow this trail generally north-northwest and follow the left side of Lady of the Lake, a pretty resting point.  Shortly after the lake, you'll reach a three-way junction and you need to stay right.  

Continue north until a stream, and even though the most obvious trail follows the stream, you need to cross and look for the less obvious trail on the far side.  Continue following this north and northwest.  From here it's another three-quarters of a mile to your next stream crossing.  Cross this one too and follow the trail north again.  You'll see from my data that we followed the obvious trail, which slowly turned east, but then turned back because we knew it wasn't right.  Stay heading north along a faint trail.  Once you are in a canyon of sorts, you'll see "heartbreak hill," a huge gully that'll take you from your current elevation of about 9,000' up to about 10,000' in about a mile, approaching on your right.  

This trail, which follows a stream, will alternate between damp dirt trail and easy boulder hopping.  The trail, faint at times, turns right (northeast) to meander through steepening woods.  Eventually you'll be on "heartbreak hill" and you'll know it.  The route it pretty obvious up this gully until Lower Aero Lake, at which point turn left and follow the west and north shores of the lake.

Look for a creek on the far side when you arrive at this lake, for your route to Upper Aero Lake.  It's between two cliffs that you can see from the southwest side of the Lower Lake when you first arrive.  Be sure not to traverse too high on the left side, as you'll be forced to downclimb just a little bit, once you inevitably see the trail on the other side of the creek, as I did.

Follow the faint trail along this creek to Upper Aero Lake.  By now you should be looking for a place to make camp.  There are plenty of flat areas along the shores of both Upper and Lower Aero Lakes.

Pass Upper Aero Lake on the south and east sides.  Look across to the saddle between a few spires called the Villard Spires and an unnamed peak to their right; that is your way to Granite Peak, whose view is just obscured by the spires.  Circumnavigating Upper Aero Lake requires some tiring rock-hopping and if you're unlucky about the route you pick, some steep scree fields.  It took me an hour to get from our campsite at the Upper Lake outlet to the top of this saddle.  Once at the top of the saddle, Granite Peak, as well as your route to it, will be obvious to the north-northwest.  Follow the running waters up the glacial canyon to various fill-up spots and finally to the last lake (unnamed as far as I can tell) before your final ascent.

The Climb

If you are uncomfortable with exposure, now would be the time to either rope up, or call it a successful backpacking trip already filled with spectacular landscapes, and head back to camp.  The last three quarters of a mile are steep, sometimes loose scrambling.  There is a large smooth-looking rock surface about a third of the way up the south face, called "the slab."  Follow the obvious "snow tongue" up to the bottom right corner of this slab.  You can climb the rocks to its left as well.  Skirt the bottom of the slab, heading north-northeast, until you can look up to your right and see a rather wide and climbable couloir that will take you almost to the top.  This is called the southwest ramp.  If you keep going north-northeast instead, you'll end up in the couloir that is actually named "southwest couloir," and it is more exposed and challenging, and therefore less favorable. 

If you've made it this far, you can probably trust your route-finding and climbing ability to pick a path to the top that you feel comfortable ascending.  Three points of contact at all times and a helmet on your head should do the trick.  At the top of this ramp, you'll reach a drop off into a steeper couloir called "the gash," at which point just scramble left along the ridge until the summit proper.  The highest point is to the east, where you'll find a summit log and USGS summit marker hammered into the highest rock.


  • Be just as careful on the way down, if not more careful.
  • I liked making this a two-day trip, but we made it back to our tent at Upper Aero around 3 and easily could have been back to our cars before dark.  Overall it was from 5pm on Friday afternoon to 11am on Sunday morning.
  • Upper Aero Lake is FREEZING.  If you want to take a dip, make sure you have dry clothes to get into afterwards.
  • Rock hopping along the lakes in the canyon leading up to Granite Peak was probably my favorite part of the trip.  They are all about a foot above the water and a good distance apart to make you feel like you are walking on water.
  • Wait until August for the snow cover in the couloirs to be low enough to ascend.  Along the canyon below, the snow fields are still solid enough to descend on, saving you quite some time and a whole lot of effort on your knees.
  • There are some ropes fixed on the route to aid you, if you so choose.  
  • Thunderstorms are a worry in the afternoon, and one hit us around 5pm when we were back in camp.  Just get back down below the saddle I mentioned before storms become a worry.


  • First views of Lower Aero Lake
  • Crossing a creek just before Upper Aero Lake
  • View of Granite Peak from canyon below
  • The last lake and fill-up spot before summiting
  • View back down the southwest ramp from above
  • Making use of snowfields on descent
  • Great view on the way down
  • Me + summit view
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