In its second annual edition, Boulderthon drew runners from all 50 states as well as 15 countries, as the signature marathon showcased the world-class city of Boulder set at the foothills of the spectacular Flatirons.

In 2023, Active named Boulderthon as one of the Top 5 Best Half Marathons in the United States.

“Racing in Boulder, Colorado, should be on every runner's bucket list, and the Boulderthon Half Marathon might be the perfect way to cross it off. The course starts at Boulder Reservoir, which gives you a true sense of Colorado's scenic beauty. Then you run along the foothills of the Flatirons. Finally, you wind your way into downtown Boulder and finish on the historic Pearl Street Mall. Veteran runners have touted this as one of the best race events of their lives; it has all the amenities of a big race (gear check, pace groups, plentiful aid stations) with the charm and attention to detail of a small race. Plus, it's a downhill finish!”


"Well Done. I’ve run nearly 50 marathons and/or half marathons and this ranks among the very best. Race day execution was flawless and I echo the previous comments about the professional staff and well organized volunteers groups. Looking forward to next year already!" 


"Great Day, Great Race. I can’t imagine a marathon that is run any better. Everything went well, volunteers were plentiful and helpful, aid stations were great, and the weather was perfect for a long run. And Boulder turned out in force to cheer us on." 


"This was my 1st half marathon race and I had a blast! Everyone was in a great mood and the course was beautiful! Thank you all!" 


"This was by far one of the best races I’ve participated in - Aid stations were dispersed well and there was so much help and encouragement from the volunteers and police officers. Thank you thank you thank you." 

95% of runners would recommend to their friends, with #1 reason being Downtown Finish & Course Views.

Read more reviews here.