Boulderthon, presented by PUMA, has announced new courses for the 2025 running event taking place on September 28, 2025. Both the marathon and half marathon routes will take participants on new journeys to some of Boulder’s most popular training routes.
All distances will still feature the start and finish line located on Pearl Street Mall in Downtown Boulder. Boulderthon’s half marathon course will take participants through different landscapes, with views of the Flatirons along the way. The marathon will expand from the half marathon course, taking participants on North 51st Street past the Boulder Reservoir and along Boulder County backroads frequently used by training Olympians, before looping to return for the Pearl Street Mall finish.
Both the 13.1-mile and 26.2-mile distances have also cut overall elevation gain. The marathon net elevation gain will be cut by about 40%, going from 982 feet to 603 feet, and the half marathon elevation gain will be cut by almost 50%, going from 384 feet to 203 feet.
“The new course was designed with both the runner’s experience in mind, and the opportunity to showcase the one-of-a-kind running trails found only here in the Boulder area,” said Alexa Squillaro, Event Director of Boulderthon.
“These new routes will give participants an even more enjoyable experience, down to the ease of the paths to the unique sightseeing throughout the whole journey. Boulder is a terrific place to explore, and with this new route, we strongly believe Boulderthon will solidify itself as a true destination race.”
The new course was designed in partnership with Boulderthon’s head coach, Nell Rojas, and Boulderthon’s city and county partners.
Nell Rojas is an American marathon runner with top American finishes at both the 2021 and 2022 Boston Marathon, a top 10 finish at the 2022 New York City Marathon and 2020 Olympic Marathon Trials and success in claiming a 10-mile US Championship title and victory at Grandma’s Marathon.
Beyond her own athletic pursuits, Rojas champions inclusivity within the running community, advocating for people of colour and promoting women.
“Its been so amazing working with our local city and county partners on designing a course that will highlight even more of the beauty within Boulder County,” said Nell Rojas, Hhead Coach at Boulderthon.
“We put a lot of thought into these routes, and feel great about their debut!”
Boulderthon, presented by Puma, offers five distances for participants to take part in, the marathon, half marathon, 10K, 5K and Kids Run.
The 10K course will run participants through the streets of Boulder, showcasing the scenic town, before leading them to Downtown Boulder for the finish on Pearl Street Mall. The second annual Heart to Heart 5K by BCH features an all-road, fast and flat experience for all participants, allowing wheelchair athletes and those utilizing wheeled vehicles, such as duo runners, to take part in the event.
Last year, Boulderthon drew nearly 10,000 runners from all 50 US states as well as 22 countries. This secured its entry into the list of the top 100 largest running events in the USA, as reported by RunSignUp. In 2023, Active.com named Boulderthon one of the Top Five Best Half Marathons in the United States, and the following year the 5K and half marathon courses were both named a top 10 in their categories by USA Today’s 10Best Readers’ Choice awards.
