Friday, September 13, 2024 | 11:00 AM Start

The Rut 21K is the perfect addition to our series of races as it fills the very large gap between our 11K & 28K race experiences.  For the Rut Runner looking to level up from the 11K, but is not quite ready for the 28K, or who simply wants to run a beautiful and challenging course on the flanks of Lone Peak, this race is for you. While this race still has a lot of climbing and descent (approx. 4000 ft) it does not traverse the exposed and rugged ridgelines of lone peak like the Rut 28K and 50K.  Instead, this course utilizes many of Big Sky’s best single-track trails creating one big loop that plays along the border of the subalpine and alpine areas of the mountain.  

OnX Backcountry 21K Map

Aid Stations & Cut-off Times (We are a cupless event)

There are 3 fully stocked aid stations along the 21K course. Each aid station will be supplied with water, Skratch Labs goodies, sweet and salty snacks, first aid, and energetic volunteers!

  • Challenger: (Mile 2.85) (Cut off time of 1:15 PM)
  • Swiftcurrent: (Mile 5.65) (Cut off time of 2:30 PM)
  • Andesite: (Mile 9.25) (Cut off time of 3:45 PM)
  • Finish Line: (Mile 13.4) (Cut off time of 5:15 PM)
  • Cut-off times will be strictly enforced for the safety of the runners and the volunteers.

Skratch Labs products you can expect on the course:

Anytime Energy Bars:
  1. Peanut Butter + Chocolate Chip (new flavor!)
  2. Cherries & Pistachios
Sport Energy Chews
  1. Raspberry
  2. Blueberry (caffeinated) (new flavor!)
Sport Hydration Mix
  1. Lemon & Lime
  2. Raspberry limeade (caffeinated) (new flavor!)

By the Numbers

  • 13.4 Miles | 21.5 Kilometers
  • 4000  ft. | 1220 Meters of elevation gain
  • Low Point: 7,500 ft | 2286 Meters
  • High Point: 9,801 | 2988 Meters
  • 3 Aid Stations
  • 1 day of making great memories in the mountains!



  • All 21K finishers will receive a unique finishers award.
  • Age group awards for age groups (Under 20, 20-29,30-39, 40-49, 50-59, 60-69, 70+)
  • Podium ceremony with awards designed by a local artist for our top three overall men, women, and non-binary athletes.


To limit congestion on the course, the 21K will have wave starts. When participants sign up they share an estimated finishing time for their event. We then assign waves based on their estimated finishing time.  We will send an email out to runners with their assigned wave. Also, runners’ waves will be on the back of their bib.  Runners must start in their assigned wave.  Help us in limiting congestion on the trails. Thank you!

*Overall awards will be based on the time from when the gun goes off with the first wave. Age group awards will be based on chip timing.



Crewing of runners is not allowed. You are, however, highly encouraged to get out on the course and see your runners as much as possible and cheer for them! Learn more about spectating opportunities on our spectator page.

21K Course Markings (Pink Pin Flags)

This is not an orienteering race. The race organizers will do everything they can to have the course marked well for race participants on the day of the event. Runners must stay on the trail. No switchback cutting! The 21K will be marked with pink pin flags.

Course Reconnaissance

We welcome you to check out the Rut course prior to the event, but please be aware that you cannot go on downhill mountain biking trails other than on race day. It is unsafe to do so. Also, in 2023 the Bonecrusher ridge climb to the summit will be closed due to tram construction.  Please check out Big Sky Resorts’ summer trails map to see what trails allow running and hiking before heading up to the resort.


Please be prepared for any type of weather. Though weather in Big Sky is relatively mild and stable in mid-September historically, we are still in the mountains and conditions can quickly change. This is a challenging run on challenging terrain and the race organizers reserve the right to stop the race at any time, should they deem the course unsafe due to weather. The race organizers will have a 28K Plan B course, which will not take race participants into exposed alpine terrain, should extreme weather exist on race day.


21K Rut Rules

  • Learn more about all Rut Rules HERE

Rut Registration Policy

  • There will be no deferrals, credits, transfers to other runners, or waitlists for any Rut race. No exceptions.
  • Rut Runners who must drop out due to unforeseen circumstances may do so by June 1st and will receive a 50% refund.
  • Rut Runners in some races may also move down in distance. This must be done no later than August 15th.
  • For example, the 50K can move to the 28K, 21K, or 11K, but not the VK.  The 28K can move to the 21K, or 11K, but not the 50K or VK. The 21K can move to the 11K, but not the 50K, 28K, or VK. The VK can move to the 11K only. The 11K cannot transfer to another event. A transfer in distance will be charged a $5 processing fee.
  • Pregnancy deferral policy - If you become pregnant, or adopt a child, after registering for a Rut race and cannot participate you are able to defer your race entry for up to 2 years. To defer, you must contact the Rut Registration Director ( no later than 30 days prior to race day.  
  • Questions? Check out our Rut Registration FAQ's page.

Thank you to our generous Rut partners!

The North Face logo
Sapphire Physical Therapy logo
Big Sky Resort logo
YETI logo
Black Roasting Coffee Co. logo
Darn Tough logo
Currex Insole logo

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