Next race
Sunday, 26 September 2027
7:00 am start
Distance
42.195 km / 26.2 mi
Urban and foothills road
Elevation
Hilly · 258 m gain
258 m climbing
Race profile
The Boulderthon Marathon draws approximately 1,500 finishers each September on an urban and foothills road in Boulder, United States. Its branding and local support turned it into a fast-growing Rocky Mountain marathon almost immediately. The course passes Pearl Street, CU Boulder, and open roads beneath the Flatirons with broad Front Range views. Rolling terrain with moderate climbs shapes the middle miles.
Boulderthon Marathon is a certified 42.195 km (26.2 mile) marathon — the standard World Athletics marathon distance.
Approximately 1,500 finishers
Course & terrain
Starts and finishes near downtown Boulder and the civic park area. The course passes Pearl Street, CU Boulder, and open roads beneath the Flatirons with broad Front Range views. Rolling terrain with moderate climbs. Rolling terrain with moderate climbs shapes the middle miles.
The Boulderthon Marathon course is hilly over 42.195 km (26.2 miles). Runners cover 258 metres of climbing and 258 metres of descent, with minimal net elevation change from start to finish.
Hilly · 258 m gain — approx. 1,624 m above sea level
↑ 258 m · ↓ 258 m · net 0 m
Registration
The Boulderthon Marathon uses open online registration at boulderthon.org with no ballot or qualifying time required. Sign-up for the September race typically opens the previous year and places are allocated first-come, first-served. Tiered pricing increases closer to race day, and charity bibs are available through partner organisations when general entry closes.
Getting there
Denver (BJC)
Rocky Mountain Metropolitan Airport
18 km / 11 mi
Common questions
Official resources
Last updated 11 October 2026. Edition dates and course details are reviewed regularly.
Close to this race
Other races closest to Boulder.
The Denver Colfax Marathon attracts approximately 2,178 finishers each May along America's longest continuous main street — Colfax Avenue. The course follows the full 42 km of Colfax from the eastern plains through downtown Denver to the western foothills at 1,600 m altitude. May's Mile High City spring and the iconic Colfax Avenue strip make it one of Colorado's most distinctive urban marathons.
Next race: Sunday, 23 May 2027
The Colorado Marathon draws approximately 1,800 finishers each May on a canyon point-to-point road in Fort Collins, United States. It delivers a scenic mountain-canyon descent without the extreme grade of some western downhill marathons. The course follows the Cache la Poudre River, red-rock canyon walls, and the approach into northern Colorado neighborhoods. The route is net downhill overall.
Next race: Sunday, 2 May 2027
The Med Bow Rail Marathon draws approximately 45 finishers each May on a scenic trail road in Laramie, United States. Laramie's Med Bow Rail Marathon uses a rail-trail corridor through southeastern Wyoming's high country. The course follows the Medicine Bow Rail Trail through high-plains and mountain-foothill scenery. Rolling terrain with moderate climbs shapes the middle miles.
Next race: Sunday, 2 May 2027
The Casper Marathon draws approximately 89 finishers each June on a scenic road in Casper, United States. Wyoming's fast-growing Casper Marathon is a USATF-certified Boston qualifier in the heart of the state. The course follows Casper river trails, prairie roads, and wide-open Wyoming vistas. Gentle undulations are the only breaks on an otherwise flat profile.
Next race: Sunday, 6 June 2027
The Run with the Horses Marathon draws approximately 57 finishers each August on a scenic road in Green River, United States. Green River's Run with the Horses Marathon serves southwestern Wyoming on a rolling high-desert course. The course tours Green River neighborhoods and high-desert plateau roads. Rolling terrain with moderate climbs shapes the middle miles.
Next race: Sunday, 1 August 2027
The Deadwood-Mickelson Trail Marathon draws approximately 238 finishers each June on a scenic trail road in Deadwood, United States. South Dakota's largest running event by participation finishes in the historic landmark town of Deadwood. The course follows the crushed-limestone Mickelson Trail through Black Hills forests, creeks, and mining-country scenery. Expect significant climbs on this hilly course.
Next race: Sunday, 6 June 2027
Planning guides
Practical guides to help you plan, train for, and run this race.
What flat, rolling, and hilly really mean — and how to read elevation gain, net change, and altitude on a marathon course.
How temperature, humidity, wind, and rain affect marathon performance — and how to use typical race-day weather when choosing a start line.
Match a race to your goals — personal bests, sightseeing, atmosphere, or a major milestone — using course data and realistic expectations.
