I’m super proud of this one – 16.1 miles (17.4 miles if you count the return trip back down Mt. Sanitas after finishing) and 5,674 feet of elevation gain in 8 hours of hiking. The Boulder Skyline Traverse is a classic hike/trail run that traverses the five tall peaks in the Boulder foothills: South Boulder Peak, Bear Peak, Green Mountain, Flagstaff Mountain, Mount Sanitas.
I started this morning at 10:40am at the South Mesa trailhead and climbed up to South Boulder Peak via the Mesa Trail and Shadow Canyon Trail. I made the decision to do the hike from south to north specifically to get the worst climb of the day out of the way early (or so I thought) – the trail through Shadow Canyon essentially goes straight up, gaining 1,600 feet in 1.2 miles (an average grade of 27%), and is an absolute asskicker.
Eventually, you reach the top of Shadow Canyon and are standing on the saddle between S. Boulder and Bear Peaks.
Relief at the top of Shadow Canyon. At this point, I had gained 2,500 feet in just over 3 miles. 
Looking left to S. Boulder Peak 
Looking right to Bear Peak
Peak #1 – South Boulder Peak – 12:43pm
From there, I headed back down S. Boulder Peak, across the saddle, and up the short connector trail to the north side of Bear Peak’s summit. I scrambled up the boulders on the summit block, and checked Peak #2 off at 1:08pm.
I then scrambled back down the summit block and headed down the Bear Peak West Ridge trail – the first big descent of the day, losing 1,200 feet in just under 2 miles. The trail crosses a creek in Bear Canyon, where I had tentatively planned to refill my 2x 1-liter LifeWater bottles… but I wasn’t in too much trouble when I arrived to find it frozen solid.
Shortly after the creek, I took a hard left onto the Green-Bear trail and started a leisurely ascent up Green Mountain. After about 500 feet of gain, I turned right onto the Green Mountain West Ridge trail, which took me to the top of Peak #3 – Green Mountain at 3pm even.
From the summit of Green Mountain, I backtracked down the West Ridge trail and then turned right onto the Ranger Trail to descend down to Flagstaff Mountain. Descending the Ranger Trail took a hot second because it was steep and shadowy, meaning it was covered in ice. Before long, I was passing the Green Mountain Lodge and crossing Flagstaff Road for a short jaunt up the Ute Trail and to the summit of Flagstaff Mountain. The actual summit isn’t marked, and the highest point is described as a rock formation that resembles a molar… which I think I found? Peak #4 – Flagstaff Mountain at 4:07pm.
I was quickly running out of daylight (sunset was 5:04pm) and had the longest section between peaks to travel. I started down the Flagstaff Trail and turned onto the Viewpoint Trail at Panorama Point. After descending all the way back down into Boulder, I walked through Eben G. Fine Park where I refilled my water from a bubbler, put on my headlamp, and put on my rain jacket as an additional layer. After crossing through a tunnel, I hiked through Settler’s Park and down the hill to the Mount Sanitas Trailhead.
At this point, the sun had set and it was fully nighttime – I was hiking by the light of my headlamp. I started up the trail to the last peak, peak #5, Mount Sanitas via the Mount Sanitas Trail. And ya’ll, this was another absolute asskicker, for a few reasons: one, it’s objectively a steep hike as it gains 1,200 feet in 1.3 miles; two, it’s a steep hike when you’ve already hiked 15 miles; and three, I was doing this trail for the first time in the dark, by myself, with a headlamp. I dragged myself up that trail, getting lost a few times (thanks runner Kevin for leading me through a tricky section!), and seriously considering turning around as I was exhausted and knew that the descent would be just as rough.
But I couldn’t resist looking at my progress on the GPS, and, knowing I was SO CLOSE, decided to push on, and touched the sign at the summit with the loudest “fuck yeah!” howl I could muster at 7:08pm. I was so proud of myself, so happy I kept pressing onwards, and so in awe that I had just completed the traverse.
I stayed at the summit of Sanitas for a few minutes, enjoying the fantastic views of Boulder’s city lights, and then I headed back down the way I came. And it was a PAINFUL descent… and truthfully, it was more of a 1.3 mile controlled fall down the very steep and rocky trail. I arrived back down at the trailhead at 8pm, called a Lyft, and settled in for a 20 minute ride back to my car.
Things I’ll Do Different Next Time
I would like to hike the traverse again (maybe in the opposite direction), maybe with a group. I’m very happy with how the hike went, but there are a few things I’d change:
- START EARLIER! 8am at the latest (from either end)
- Bring water filtration – I passed a number of smaller streams along the way, but they weren’t moving fast enough for me to feel comfortable drinking it fresh
- Remember my sunglasses! Whole lot of good they did me back in the car…
- Attempt to hike Shadow Canyon with fewer breaks / a slower pace.
- Consider ascending/descending Mt. Sanitas via the Lion’s Lair trail. The standard route is just painful.
Thanks for reading!
