The Boulder Skyline Traverse is a 18+ mile hike or trail run located just outside of Boulder, Colorado. You can tackle this route in a number of ways but the most popular way is to go South to North. The trail starts at the South Mesa TH works up to South Boulder Peak, Bear Peak, Green Mountain, Flagstaff Mountain and ends at the summit of Mt Sanitas before descending back to that TH. There are a ton of variations to this hike but the most common one is 18 miles long with 6,000ft of vertical gain – a very tough day.
Boulder Skyline Traverse Quick Facts
Virtual Trail Guide: Boulder Skyline Traverse
Boulder Skyline Traverse Rating: ★★★★★ (5/5 Stars)
Distance: 18+ Miles Rt
Elevation Start: 5,620ft
Highest Elevation: 8,455ft
Total Elevation Gain: 5,951ft
Estimated Time to Complete: 6-12 Hours (Running vs Hiking)
Difficulty: Strenuous What does this mean?
Class: Class 2/3 (very minor sections on Bear Peak) – What does this mean?
Season: Year Round – Best Time to hike is spring or fall
Directions to Boulder Skyline Traverse
Trailhead: South Mesa Trailhead
Getting Here: From Highway 93 just south of Boulder, take Eldorado Springs Dr and continue for 1.6 miles to reach South Mesa TH on your right. If that lot is full, you can also try Doody Draw TH right across the street.
Parking: This area is almost always crowded and parking is usually going to be a huge problem if you arrive late. On weekends, the lot will fill by 8AM, sometimes earlier. Plan to be dropped off here, especially if you are doing a one way hike/run – it will make your day much easier.
Fee: As of 2022 – there is a $5 fee for this hike if you are NOT a Boulder resident with cash and mobile app options to pay. However, for Verizon I had no luck with service and was glad I prepaid on the app before arriving. Boulder residents are free.
Dogs: This is a dog friendly hike, but dogs must be kept on a leash. Boulder is VERY strict and finicky about dogs – particularly where they are allowed on and off leash. This map talks more about it.
Camping: Camping is prohibited anywhere in Boulder Open Space.
Water: There are a few unreliable and seasonal water sources that you pass by on this hike but in general, it’s best to just be self sufficient.
Make it a Loop: As mentioned above, this is a one way hike with several options to add your own variations, distance and even make it a complete loop if you really like suffering. View a full map of the area here.
Trail X Factors: Trail Near Each Peak
I am not a good trail runner. I am very mediocre and slow. However, I would find it very surprising if trail runners at any level would be able to run the terrain around all of the mountains you summit on this trail with the exception of Flagstaff Mountain. Running or hiking, the trail is very busy, narrow and in some sections extremely technical (lots of rocks, roots, loose gravel and STEEP). In addition, if you hike this route from south to north, the Shadow Canyon Trail is downright brutal in its grade and technical terrain. It sucks the life out of you on its way to gaining just about 3,000ft.
Hike Tip(s): SAVE.YOUR.LEGS & Fuel Early
Whether you are trail running or hiking – both tips apply here: save your legs for later in the day and get calories and hydration into your body early. I bonked very hard on Mt Sanitas (super steep hike on its own) and regretted not consuming more calories earlier in the day. Luckily, my legs had a lot of juice left though which made the run down the mountain enjoyable. In addition, you will not want to hike or run this on a day where temperatures are over 75 or so degrees, it will turn into a suffer fest very quickly.
Best Views: I really enjoyed most of the views on this run, but my favorite were from South Boulder Peak to the trail just before Green Mountain. You left many of the crowds behind, felt extremely deep into nature and had awesome views into Indian Peaks Wilderness to your west. This was without a doubt my favorite section of the trail.
Boulder Skyline Traverse South to North Route
- Men’s Trail Runners
- Women’s Trail Runners
- La Sportiva Trango Hiking Boots (Men’s)
- La Sportiva Trango Hiking Boots (Women’s)
- Backpack or Trail Running Vest
- Food & Water
- Protection from the Sun
- Map of Area – take a pic at the TH map – very important with so many trail junctions
- Optional: Water Filter
- Optional: Garmin inReach
- Optional: Hiking Poles
- Optional: Garmin Fenix Watch
- Optional: Camera and Lens
- Optional: GoPro, Joby Tripod
- *Links included in this description might be affiliate links. If you purchase a product or service with the links that I provide I may receive a small commission. There is no additional charge to you.
My Trip to Boulder Skyline Traverse: April 2022
April of 2022 was proving to be a real fickle bitch of a month. Every week I looked forward to the weekends so I could get into the mountains and every week the weather greeted me with shit. High winds or heavy snow =not the best time when you need to be logging serious miles for ultra marathon training. Mother nature gives you lemons and you make lemonade or in my case, get lucky how many awesome options there are in Colorado. I drove to the South Mesa TH after planning a pick-up time with my wife Jackie and my day almost didn’t start before it even started. Luckily, I got the last spot in the parking lot after a mountain biker left for the day.
The hike up South Boulder Peak (the first one of the day) was brutal with no warmup. I had hiked these trails before, but forgot how tough they were! It was a relief to finally summit South Boulder Peak and know that Bear Peak was nearby – knocking down 2 of my 5 summits of the day. I didn’t spend much time on either summit because I had over 15 miles of running still to go with over 3k of vertical gain left as well. After working down Bear Peak, the runnable terrain picked up and the views to the west were amazing. This section ended quickly and I had to work up more steep and technical terrain to summit Green Mountain – my third peak of the day.
At this point, my legs were starting to feel all the hills and the day hiking crowds had certainly picked up. A short section of snow and ice slowed down my progress again before a nice runnable section on my way to Flagstaff Mountain. I was lucky to glance at my watch and notice a summit icon which I quickly figured out was Flagstaff. There was not an official trail to this summit and I wanted to be a responsible leave no trace trail runner so just moved on down the mountain.
This next section was fast on a good trail crossing a road several times and even a bathroom at the Halfway House overlook. It was crazy how much progress I had made on the day as my views of the mountains were gone and I was now overlooking Boulder. I descended some more and really enjoyed the running here. Enjoyment of the Boulder Skyline Traverse ended quickly here as my last peak of the day, Mt Sanitas was up next. You wouldn’t think much of this summit by looking at it, but it absolutely sucked the life out of me. I blame poor hydration, lack of calories and over 4k of vert on my legs – but regardless, it was a sufferfest to gain this summit.
Eventually, I dragged my lifeless legs to the summit of Mt Sanitas and looked back at the amazing progress I had made over the 16 miles of running. I was proud of myself but knew that I had a couple of miles still to go and a very technical ridge to get down to the last runnable section of trail. I worked down the East Ridge trail on Sanitas which was scenic but brutally steep and full of poor trail conditions. After filming some last minute video clips, I dragged my butt down the last bit of trail and back to the road where Jackie was meeting me.
Overall, I really enjoyed the Boulder Skyline Traverse and shameless plug to my video; I feel that it’s one of the best I have made in a while. The day was really tough, but the weather was beautiful and the views were amazing. Best of all, I tackled a bunch of new mountains on trails that I had never been on before. Quick note about North to South – I probably wouldn’t do this as you are essentially constantly climbing the entire day vs a steady downhill until you reach Sanitas coming from the south.