Welcome to the Blue Sky Trail Marathon & Half, Fort Collins's original and only trail marathon.
Taking place on the trails between Horsetooth Mountain Park and the Devil's Backbone Open Space, the course takes you on a north-south tour of the easternmost hogbacks of Northern Colorado's mighty Front Range.
The marathon boasts 3,500 feet of elevation gain/loss, while the half marathon checks in at 1,800 feet, and the route offers a little bit of something for everyone. It is designed to appeal to both veteran trail runners and those looking to experience their first trail racing adventure. The generous nine hour cut-off should ensure a successful day for everyone.
The course is 100% dirt and 90% sweet Colorado singletrack. The terrain ranges in difficulty from smooth dirt trail to technical rock gardens. A small portion of the route is on smooth dirt road (no motor vehicle access) and gravel bike path, with the meat of the running done on the beautiful and distinctive redstone hardpack of the Blue Sky Trail.
After the race, kick back and enjoy the always-popular barbecue and generous sponsor giveaways.
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Start: Blue Sky Trailhead, Horsetooth Mountain Park. Fort Collins, Colorado
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Distance: 26.7 miles (3,500') or 13.4 miles (1,800')
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Min/Max Elevation: 5,300'-6,500'
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Average Elevation: 5,700' Marathon
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Terrain: Marathon: 22mi dirt singletrack, 3mi rocky singletrack, 2mi dirt road; Half Marathon: 13.0mi dirt singletrack, 0.5mi dirt road
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Fauna: Deer, abert squirrel, golden eagle
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Registration Cap: 400 Marathon / 400 Half
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Time Allowance: 9 hours Marathon / 6 hours Half Marathon
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Dates: Marathon: Oct 17, 2026; Half Marathon: Oct 18, 2026
Trail Sisters Approved
Registration
Fees for the 2026 Blue Sky Marathon & Half Marathon are as follows:
Marathon:
Dec 15 – Feb 28: $110 + $7.60 fee
March 1– June 30: $120 + $8.20 fee
July 1 – Oct 17: $130 + $8.80 fee
Packet Pickup: $145
Half Marathon:
Dec 15 – Feb 28: $90 + $6.40 fee
March 1– June 30: $100 + $7.00 fee
July 1 – Oct 17: $110 + $7.60 fee
What You Get in Return for Your Registration Fee:
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A beautiful, challenging and well-marked course on some of the best trails in Fort Collins
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Enthusiastic, knowledgeable race and aid station volunteers
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Fully stocked aid stations
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Free entry to Larimer County Open Space for the day
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Generous Cut-Offs (Marathon: 9hrs / Half 6hrs)
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Gender specific race T-shirt
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Unique finisher award and overall and age group awards
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Finish line meal
- Vegetarian, vegan, gluten-free and non-alcoholic options are available as part of our standard race fare
- Professional medical and emergency communications
Waiting List
In the event that the race sells out, we will maintain a waiting list and transfer runners from the waiting list to the race roster should other runners already registered not be able to attend.
Transfer Credit Policy
If you are not able to race, we will be able to offer a race transfer credit that can be applied to any future Gnar Runners race (valid for 12 months). Credit deadlines are as follows:
Until March 31: 100% credit of registration (excluding RunSignup fees)
April 1 - July 31: 75% credit of registration (excluding RunSignup fees)
August 1 - October 15: 50% credit of registration (excluding RunSignup fees)
**In order to receive your credit, you must cancel your registration through the RunSignup registration platform.
Deferrals:
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Log in to your RunSignup account
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Go to Profile -> Upcoming Races -> Blue Sky -> Manage Registration
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At the bottom of the page, select “Defer Registration” and follow the automated process.
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While RunSignup will prompt you to, you DO NOT have to immediately choose which race to apply your credit to. Once you hit "Confirm Deferral" and see the "Your registration has been deferred" message, your credit is in the system and will be valid for one year past the event date.
Distance Switch:
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Log on to your RunSignup account
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Go to Profile -> Upcoming Races -> Blue Sky -> Manage Registration
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At the top, click the link to "Transfer Event"
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Follow the steps to register for the race in the new distance
Runners in the half marathon race can pay the additional registration fee to upgrade to the marathon race. There is no charge for marathon runners dropping down to the half marathon race.
The online deadline to transfer is Thursday (10/16) at midnight. It can also be done in person at packet pickup on Friday.
Cancellation & Refund Policy
Entries are non-refundable. Entries are non-transferable, except for transfers via the wait list. In the event the race is cancelled due to extreme weather, fire, disease or for some other unforeseeable event, we cannot offer refunds or credits.
Course & Aid Stations
Course Maps
Blue Sky Trail Marathon Course Map
Blue Sky Half Marathon Course Map
Course GPX Files
Elevation Profiles
Blue Sky Trail Marathon Elevation Profile Blue Sky Trail Half Marathon Elevation Profile
Marathon Aid Stations
Aid Station Mile Split Total Gain Descent Cut-Off Drop Bag Aid
Towers 4.4 4.4 1350 350 - No Fluids Only
Blue Sky (Start/Finish) 4.8 9.2 150 1150 10:00a Yes FULL
Indian Summer North 1 4.0 13.2 450 350 - No FULL
Indian Summer South 1 2.4 15.6 300 400 12:30p No FULL
Hunter Turnaround 2.3 17.9 400 250 - No Safety Only
Indian Summer South 2 2.4 20.3 250 400 1:45p No FULL
Indian Summer North 2 2.4 22.7 400 300 - No FULL
Finish 4.0 26.7 350 450 4:00p Yes FULL
Half Marathon Aid Stations
Aid Station Mile Split Total Gain Descent
Underpass 1 1.9 1.9 150 100
Indian Summer North 1 3.5 5.4 500 400
Indian Summer North 2 2.7 8.1 550 550
Underpass 2 3.5 11.6 400 500
Finish 1.9 13.4 100 150
All aid stations will offer Gnarly Nutrition Fuel2O sports drink, Hammer Gels, water and soda plus a variety salty and sweet bites, and a selection of fruit.
***There will be GF/Vegan alternatives for nearly all non-GF/V standard offerings. These are typically held back to save them for those who need them, so please ASK! Also note that while we will do our best to keep utensils and trays separated for these as well as common allergens, this is the backcountry and cross-contamination can occur.
While we will provide plenty of electrolyte options in drink mix and salty real foods, we deem the risks associated with salt in concentrated pill form to be more than we're comfortable providing. We won't restrict runners from using their own salt caps, but will not have them available at aid stations.
Time Cut-Offs
Marathon course cut-offs will be enforced at the following aid stations:
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Blue Sky Aid Station (mile 9.2) at 10:00am. 3:00 total time.
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Indian Summer South outbound (mile 15.6) at 12:30pm. 5:30 total time.
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Indian Summer South inbound (mile 20.3) at 1:45pm. 6:45 total time.
There are no on-course cut-offs for the half marathon.
Drop Bags
Marathon runners may leave a drop bag at the Blue Sky Start/Finish to pick up at mile 9.2. We will have a tarp to set bags out. Pack your gear to stay dry in case we get any rain.
Half Marathon runners may leave a drop bag at the South Bay Start/Finish. We will have a tarp to set bags out. Pack your gear to stay dry in case we get any rain.
Please provide your own bag and keep it to a reasonable size (small duffel bag or stuff sack). Clearly label it with your name and bib number. Please do not leave any valuable items in your drop bags - volunteers are not responsible for lost items. Drop bags will not be transported to any other locations on course.
Course Marking
The courses will be well marked with pink flagging and pink pin flags. Important intersections will be supplemented with flour ground markings and directional arrows. On longer stretches of trail without intersections, confidence flagging will be placed approximately every quarter mile. Turns will be marked heavily.
Toilets
There will be ample facilities at the start/finish.
We will have an additional portable toilet at the Indian Summer North Aid.
In addition, there are park facilities that can be used in the campsite between the main Marina parking area and the start for the marathon that will be passed at marathon miles 1-2 and 8-9.
Crewing & Spectating
Half Marathon
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Due to the course layout & access, there are not provisions for mid-race spectators for the half marathon.
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For the Half Marathon Start/Finish, park in the South Bay parking area.
Marathon
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Marathon runners are not allowed to receive assistance from crew on the course outside of the Blue Sky Start/Finish area at mile 9.2. No pacing is permitted.
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Much of the marathon course is run on trails that are not easily accessible to spectators. The best viewing points are the Start/Finish line at the Blue Sky Trailhead (also marathon mile 9.2 Aid), the Soderberg Trailhead, and the Hunter Loop 18-mile turnaround.
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NO Crewing is allowed at the Indian Summer North or South Aid Stations.
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For the Marathon Start/Finish, park in the Marina parking area (see above) and walk over, please do not drive through or park at the start/finish.
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To access the Soderberg Trailhead, from the Start/Finish, turn north on Shoreline Drive and make a left into the trailhead parking lot. If the parking lot is full, you may park in the Marina parking area and walk north through the campground to the trailhead.
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To access the Hunter loop (18-mile turn), drive to the Devil's Backbone Trailhead near Loveland. Take Highway 34 West from Loveland and take a right onto Hidden Valley Rd and follow signs to the Devil's Backbone parking lot. Follow the trail north up the hill to the junction of the Wild and Hunter loops (roughly 2 miles).
The entire trail system is open to the public if you would like to spectate and encourage your runner elsewhere on course; however, crewing and pacing by foot or by bike is not allowed and will result in the disqualification of your runner.
Training
There will likely be organized training runs on Saturdays in September/October for Blue Sky. See the Fort Collins Trail Runners Facebook Group for group run postings, as well as our Community Page for suggested routes.
We also offer a basic 15-week (marathon) and 9-week (half marathon) training plan leading up to the event.
Detailed Marathon Course Directions
Start to Towers Aid (4.4mi): The start line is located at the Blue Sky Trailhead off County Road 38E, six miles west of Fort Collins. From the start, you will run north on the Blue Sky Trail through the campground 1.3 miles to the Soderberg Trailhead, continuing north on the Swan Johnson Trail to Towers Rd where you will take a left up the hill to Towers Aid.
Towers Aid to Blue Sky Aid (9.2mi): Volunteers at Towers Aid will direct you out of the aid station to turn right onto the Herrington Trail. Shortly after the turn onto Herrington you will bear LEFT onto the Stout Trail (courses split). The descent down the Stout Trail is rocky, so watch your footing, though be sure to check out the reservoir views. Stout will contour around the hillside to bring you back to Towers Rd. Turn right on Towers Rd and take another right back onto Swan Johnson south back to the Soderberg Trailhead. Continue south back through the campground to the Blue Sky Aid start/finish area.
Blue Sky Aid to Indian Summer North Aid (13.2mi): Continue south on the Blue Sky Trail. This section of the trail will be winding, rolling single track with many blind corners. Please be aware that the trail is open for public use. You will pass only one trail junction with the Rim Rock Trail. Continue straight past this intersection down the hill into the valley towards Indian Summer North Aid, which will be visible from this point on the course.
Indian Summer North Aid to Indian Summer South Aid (15.6mi): The Indian Summer North Aid is at the junction of the Indian Summer Loop. Make sure that your number is recorded at the aid station and volunteers will direct you to turn right up the hill onto the Indian Summer Trail. On completing the loop, make a right at the trail junction to turn south back onto the Blue Sky Trail. Indian Summer South Aid will be located about a quarter mile south of this intersection. This is your last chance for aid before a long and difficult 5 mile section through the Devil's Backbone side of the course. Make sure you leave with adequate water.
Indian Summer South Aid to Hunter Turnaround to Indian Summer South Aid (20.3mi): Continue south on the Blue Sky Trail. Once you pop over the hogback cliff band, the terrain becomes very rocky and technical. There are two loops to negotiate here and all you need to remember is to turn right. There is only one right way to go. At the first junction with the Laughing Horse Loop, turn right. At the end of the Laughing Horse Loop, continue straight ahead. At the second junction with the Hunter Loop, turn right. At the end of the Hunter Loop, a course marshal will record your number. Volunteers hike into this location so there will be no aid available. The course marshal will direct you to continue around the Hunter Loop, and you will return north towards the finish. On the return trip at the end of the Hunter Loop, turn right and continue north. At the next Laughing Horse Loop junction, turn right. At the end of the Laughing Horse Loop continue straight north, back down off the ridge into the
valley to Indian Summer South Aid.
Indian Summer South Aid to Indian Summer North Aid (22.7mi): From Indian Summer South Aid, you will return the way you came. About a quarter mile north of the aid station, you will turn left to go back up and over the Indian Summer Loop to Indian Summer North Aid.
Indian Summer North Aid to Finish (26.7mi): After leaving Indian Summer North Aid, you’ll have a short climb up past the Rim Rock junction. From there you’ll have just a few more miles of rolling single track to the finish.
Detailed Half Marathon Course Directions
Start to Underpass Aid (1.9mi): From the start at South Bay, follow the new Bay-to-Bay Trail around the peninsula to where it joins with the Blue Sky Trail. Turn left to head south on the Blue Sky Trail to the aid station.
Underpass Aid to Indian Summer North Aid (3.5mi): Continue on the Blue Sky Trail heading south, past the junction with the Rimrock Trail to the junction with the Indian Summer Trail where the aid station is located.
Indian Summer North Aid to Indian Summer North Aid (2.7mi): Out of the aid station, head west on the single track trail, climbing steadily up and curving south around the Indian Summer Loop. Enjoy the false summit! Bomb back downhill on the single track switchbacks until you reach a T-junction with the Blue Sky Trail. Turn left (north) and follow the single track for about a quarter mile till it junctions with the gravel road. Turn left (north) and follow the road another 0.4mi back to the aid station.
Indian Summer North Aid to Underpass Aid (3.5mi): Retrace your steps back to the start/finish. Begin by heading east/north out of the aid station on the Blue Sky Trail, continuing north under the underpass to the aid station.
Underpass Aid to FINISH (1.9mi): Continue north on the Blue Sky Trail for a very short distance, veering right at the junction onto the Bay-to-Bay Trail around the peninsula and to the Finish!
Race Rules
Race rules are designed to provide a safe and fair experience for everyone involved and to help ensure our ability to produce the race again next year. Major rule infractions by racers will result in immediate disqualification of the racer. Please do not argue with or harass our volunteers. Please direct any questions and feedback to us here.
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The marathon will be limited to 9 hours and the half marathon will be limited to 6 hours. Both will start at 7:00am. Please refer to the Aid Station section of this page for intermediate marathon cut-offs. There are no intermediate half marathon cut-offs.
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At each aid station, volunteers will record runner bib numbers. Runners are responsible for making sure that aid station volunteers record their number. Please make sure that your bib number is visible from the front and call out and confirm your number when passing through an aid station. This is important so that we can keep track of runners, record your intermediate race splits and know that you are not lost or injured.
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If you need to drop out of the race for any reason, you must check out with the nearest aid station or course volunteer.
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Purposeful littering is prohibited and will result in an immediate disqualification.
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Stay on the trail. No bushwhacking or short cutting. In case of wet trail conditions, please run through any muddy sections to avoid widening the trail. Yield to pedestrian and horses. Mountain bikers should yield to runners, but please use common sense in all circumstances.
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Pacers are not allowed. Crewing is allowed at designated aid stations only.
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No mechanical aid (poles, traction devices, etc.) unless approved by race staff prior to the race for a specific reason.
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All runners should carry a 16oz minimum water bottle or bladder that can be refilled at aid stations. There will be no water cups at aid stations.
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Dogs are not allowed on the course with runners.
Schedule
Friday 10/16:
4:00-7:00p: Optional marathon & half marathon packet pick-up at Altitude Running 2531 S Shields St #2N, Fort Collins, CO 80526
Saturday 10/17:
5:30-6:45a: Marathon Race Day Packet Pickup
6:50a: Marathon Pre-Race Briefing
7:00a: Marathon Start
9:30a-4:00p: Finish Line Meal Served
10:00a: Blue Sky Aid Cut-Off - Marathon
11:30a: Overall Marathon Awards. Age Groups Offered on a Rolling Basis
12:30p Indian Summer South Aid Southbound Marathon Cut-Off
1:45p: Indian Summer South Aid Northbound Marathon Cut-Off
4:00p: Finish Cut-Off
Sunday 10/18:
5:30-6:45a: Half Marathon Race Day Packet Pickup
6:50a: Half Marathon Pre-Race Briefing
7:00a: Half Marathon Start
8:30a-1:00p: Finish Line Meal Served
9:45a Overall Awards. Age Groups Offered on a Rolling Basis
1:00p: Finish Cut-Off
Parking & Directions
Marathon
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The Marathon Start/Finish line is located at the Blue Sky Trailhead off of County Road 38E across from the Horsetooth Tavern.
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Parking for all participants and spectators will be located in the Inlet Bay Marina parking lot off of Shoreline Drive. It is a 0.7mi walk from the Marina to the start/finish area.
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Carpools of two or more runners will be given priority parking at the Blue Sky Trailhead at the start/finish until it fills. Please carpool if you can and want priority parking.
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Parking is in designated parking spaces only. There is no parking allowed in the campground areas (unless you have reserved and paid for a nearby campsite.)
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Drop offs can be made at the small turnout off Shoreline Drive just around the corner from the Blue Sky Trailhead. Vehicles should not stop anywhere on the side of 38E.
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Parking is not allowed anywhere on 38E, along Shoreline Drive, or on any connecting residential street.
Half Marathon
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The Half Marathon Start/Finish line is located at the South Bay Pavilion off of County Road 38E. Turn in at the sign for South Bay, right after the Town of Stout sign.
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Parking for all participants and spectators will also be in South Bay. Later arrivals may have a longer walk.
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Parking is in designated parking spaces only. There is no parking allowed in the campground areas (unless you have reserved and paid for a nearby campsite.)
All vehicles containing registered runners will receive a park pass - good for one vehicle - as part of their entry fee upon arrival on race morning. Any other vehicles (crews/spectators) will be required to have a Larimer County Parks Annual Pass or purchase a day pass on-site for $10.
Driving Directions
Marathon: 4780 W County Road 38E, Fort Collins, Colorado, 80526
Half Marathon: 4210 W County Road 38E, Fort Collins, Colorado, 80526