Bighorn 100 Race Guide

The Bighorn 100 takes place each June in the rugged Bighorn National Forest of northern Wyoming. In 2025, the 100-mile event is scheduled over the weekend of June 19 through June 21, with the 100 mile start typically at 9 AM on Friday, June 19. This mid-June timing often brings unpredictable mountain weather, ranging from heat waves to afternoon thunderstorms, and occasional late-season snow at higher elevations. Runners should prepare for wide temperature swings between the sunny canyon stretches and the cool, exposed ridge lines. The serene beauty of wildflower fields and river canyons contrasts sharply with the course’s toughness, making Bighorn both inspiring and daunting.

Qualification and Registration

Entry into the Bighorn 100 is open to any qualified ultrarunner, but registration is competitive due to limited field sizes. For the 2025 event, 100 mile entries opened October 15, 2024 at 6 AM Mountain Time via the official registration portal, with entries non-transferable and refunds only available at 50 percent prior to March 31, 2025. Unlike some races that use lotteries or performance standards, Bighorn admits runners on a first-come, first-serve basis, though previous finishers and volunteers sometimes receive preferential placement. Prospective participants should ensure their calendars are clear on registration opening days and have their race resumes and timing credentials ready. It also serves as a qualifying race for the Western States Endurance Run and Hardrock Hundred Mile Endurance Run, making it especially appealing for those chasing legendary Western mountain 100 milers.

Course Format and Elevation Profile

The Bighorn 100 follows a classic out-and-back format, beginning and ending near Dayton, Wyoming, with the turnaround at Porcupine Ranger Station roughly 50 miles into the course. Starting at an elevation of 4,275 feet on Tongue Canyon Road, runners climb to nearly 9,000 feet through a series of three major ascents and descents, accumulating approximately 20,500 feet of total ascent and an equal descent by the finish. The first big climb to Dry Fork Ridge reaches 7,480 feet by mile 13.5, and the final high point near Bald Mountain approaches 9,000 feet on the outbound leg. Altitude is a constant factor, with much of the course above 6,000 feet, so acclimatization and pacing are critical to avoid altitude-related fatigue and headaches.

Terrain Breakdown

More than three-quarters of the Bighorn course is single-track trail winding through dense forest and open meadows, offering technical footing and scenic vistas for about 76 percent of the distance. Approximately 16 percent of the route follows double-track or old logging roads, where runners can make up time on firmer surfaces. The remaining 8 percent consists of gravel or four-wheel-drive roads, notably on some canyon descents and at remote aid access points. Trail conditions can vary dramatically depending on spring snowmelt and summer storms, turning flat sections into muddy quagmires that have famously swallowed shoes and slowed top runners. Proper footwear choice and awareness of potential mud pits are essential, as is readiness for creek crossings and slick rock slabs.

Key Challenges

The Bighorn 100 is notorious for deep, shoe-sucking mud that can sap strength and morale on long, slow slog sections. Weather extremes from hot, dry canyons to cold, windy ridges create a rollercoaster of conditions that test gear choices and runner adaptability. Steep climbs early in the day under strong sun can lead to dehydration, while long descents and night running challenge muscles and navigation skills. The remoteness of aid stations, with the most accessible at Dry Fork and Porcupine, means runners must be self-sufficient between stops and carry adequate water, nutrition, and emergency gear. Wildlife encounters, including moose on single track, add an unpredictable element, underscoring the need for alertness and wildlife etiquette.

Time Limit and Cutoffs

Runners have an overall time limit of 34 hours to complete the 100 mile distance, with the clock starting at the 9 AM gun on race day. Intermediate cutoffs enforce safety and pace: runners must pass Dry Fork Ridge (mile 13.5) by 3 PM on race day and reach Sally’s Footbridge (mile 30) by 8:30 PM, or face disqualification. The turnaround at mile 50 looseens logistical constraints but still requires runners to maintain the minimum pace to make the 34 hour finish. Volunteers and aid crews are stationed strategically, but the course’s remoteness means missing a cutoff leg can leave a runner stranded in rough terrain. Adhering to cutoff times and having a solid pacing plan are vital to a successful Bighorn finish.

Aid Stations

The Bighorn 100 features thirteen aid stations spaced to offer critical support throughout the out-and-back route. Runners leave the start at Tongue Canyon Road (mile 0) and quickly reach Tongue River Trailhead at mile 1.25, before following a sequence of Lower Sheep Creek at mile 3.5, Upper Sheep Creek at mile 8.5, and Dry Fork Ridge at mile 13.5. From there the course passes Kern’s Cow Camp at mile 19.5 and Bear Camp at mile 26.5 before reaching Sally’s Footbridge at mile 30. The turnaround at Jaws Trailhead at mile 48 marks the halfway point and is one of the easiest stations to access by crew. On the return leg runners again pass Spring Marsh, Cathedral Rock, Sally’s, Bear Camp, Kern’s Cow Camp, Dry Fork Ridge, Upper Sheep Creek, Lower Sheep Creek, and Tongue River Trailhead before the Home Stretch at mile 98 and the Scott Park finish at mile 100. Dedicated drop‐bag locations are available at Sally’s Footbridge, Jaws Trailhead, and the finish, enabling runners to replenish clothing and gear exactly when they need it. Crew access points include Tongue River Trailhead, Dry Fork Ridge, Sally’s Footbridge (high‐clearance vehicle recommended), and Jaws Trailhead, with volunteers staffing every station to ensure supplies, medical support, and encouragement are always at hand.

Mandatory Gear

Bighorn’s mandatory gear list is designed to keep runners safe through fluctuating mountain conditions. Every participant must carry a functioning headlamp plus spare batteries to cover night‐time miles on uneven terrain. Runners are required to have gloves and a buff to protect against sudden cold snaps or wind chill on exposed ridgelines. Warmer layers such as a lightweight insulated jacket and waterproof rain shell must be carried, ensuring warmth during late‐night descents or unexpected storms. All runners must wear reflective bibs and have sufficient water‐carrying capacity to reach the next aid station in case of delayed crew access. Drop‐bag tags provided by race organizers must be attached to all gear bags, and runners should check that batteries, nutrition, and first‐aid items are securely stored before the start.

Crew and Pacing

Support crews are welcome at all main aid stations, though they must remain within 100 yards of each station’s footprint and cannot shuttle runners between stations by vehicle. Crews may access Tongue River Trailhead, Dry Fork Ridge, Sally’s Footbridge, and Jaws Trailhead by car, with high‐clearance vehicles recommended for the Sally’s approach. Pacers are permitted to join runners after the Jaws turnaround only, helping to maintain pace and morale through the toughest second half of the course. Vehicle traffic is strictly controlled on single‐track and remote forest roads, so crews should plan logistics carefully and avoid driving off designated access routes. Runners should coordinate drop‐bag and crew schedules in advance to minimize downtime and ensure they hit cutoff times en route to a successful finish.

Navigation

The Bighorn 100 course is marked with bright orange flags, reflective ribbons, and prominent trail signage at every junction, guiding runners through canyon bottoms, forested single‐track, and alpine ridges. Despite these markers, thick fog or heavy storms can obscure the trail, so participants are strongly encouraged to carry a GPS device loaded with the official race GPX file. Course marshals periodically monitor critical waypoints, but self‐navigation skills remain essential in remote sections where flagging may be blown down or covered by snow early in the season. Compasses and topographic maps are not required but may serve as reliable backups. Runners should review the course profile and station locations beforehand to visualize pacing and identify potential navigation hazards.

Finish Rates

Historically, the rugged nature of Bighorn yields a finish rate of roughly 50 percent among starters, reflecting its status as one of the most challenging trail 100-mile races in the United States. Factors such as deep mud, steep climbs, night running, and altitude combine to push many entrants to drop at key cutoffs like Dry Fork Ridge or Sally’s Footbridge. Weather variability—ranging from scorching canyon heat to sub‐freezing temperatures on Bald Mountain—further impacts completion percentages. Although stronger fields and improved gear have nudged rates upward in recent years, Bighorn remains a formidable test where even experienced ultrarunners must fight hard for the coveted finisher’s buckle.

Special Features

The Bighorn 100 stands out for its combination of wild Wyoming scenery, shoe-sucking mud pits, and the Rocky Mountain Slam qualifier status it offers. Finishers earn a distinctive silver buckle emblazoned with the race’s mountain silhouette, symbolizing their conquest of 20,500 feet of climbing and descent. The race’s volunteer “trail family” is celebrated for creating a life-changing experience both for runners and crew, with many volunteering year after year. Record-holders like ultrarunning legend Karl Meltzer have cemented Bighorn’s reputation by setting blistering course times, yet the event’s ethos remains rooted in camaraderie and environmental stewardship of the Bighorn National Forest.

Previous Winners

The elite history of Bighorn showcases repeat champions who have mastered its unforgiving terrain. Karl Meltzer, widely regarded as one of the greatest ultrarunners, has captured multiple 100-mile titles here, setting the male course record under 20 hours. On the women’s side, Barb Mileham and later Nikki Kimball have each stood atop the podium, posting sub-25 hour finishes. Recent editions saw rising stars such as Mike Wardian and Christy Pflug adding their names to the roll of honor, demonstrating that peak performance at Bighorn demands both speed and endurance in equal measure.

Official Contact Information

For race questions, registration assistance, or volunteer inquiries, reach out to Race Director Cheryl Sinclair by email at racedirector@bighorntrailrun.com or by phone at 307-673-7500. The organizing team, based in Sheridan, Wyoming, also maintains a detailed FAQ and resource library at www.bighorntrailrun.com to guide entrants through every step of their Bighorn journey.