Colorado Triathlete

Three Creeks Half Marathon
2026-04-05 | Bear Creek Lake Park (Lakewood), 15600 W. Morrison Road, Lakewood, CO, 80228, United States
Racing Underground brings you an amazing half marathon this spring! The Three Creeks Half Marathon features a half marathon course that is flat, fast and scenic!
Travel on foot through some of the most beautiful parts of Cherry Creek State Park, with a total combined elevation gain of only 291 feet spread out over 13.1 miles as the course follows the banks of Cherry Creek, Windmill Creek, and Cottonwood Creek on a mix of road, paved running trail, and wide dirt trails.

Boulder Rez Half
2026-04-11 | Boulder Reservoir, 5275 Reservoir Road, Boulder, CO, 80301, United States
This spring race features a spectator-friendly Half Marathon, 10K and 5K course. Attracting athletes from all over the west due to its phenomenal scenery, glamorous finisher medals, perfect running temperatures with many nearby Boulder attractions to enjoy after the race.
The run course loops around the Boulder Reservoir and remains mostly on dirt trails. The course is flat with only 200 feet of elevation gain. You will experience iconic views of the mountain range to the west.
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The Half Marathon will complete 2 loops, and the 10K will complete one loop. 5K runners will take a different course route.
The Half Marathon is now a USAT Certified Course.

NOCO Half Marathon & 10K
2026-04-25 | Boyd Lake State Park (Loveland), 3720 N County Road 11-C, Loveland, CO, 80538, United States
Spring is the season of renewal and running. We hope you join us for a fun adventure that embodies the spirit of springtime at the beautiful Boyd Lake State Park!
Choose from the Half Marathon (13.1 mile) or 10K (6.2 mile) for your run adventure. This course is on smooth paved walkways with about three quarters of a mile being off road. Beautiful lake and wildlife views and fun post race festivities. Did we mention almost no elevation gain? This is one flat course making sure you’ll set a new PR or enjoy a fun steady-paced morning run race

Timberview Trail Run
2026-06-27 | Boyd Lake State Park (Loveland), 3720 N County Road 11-C, Loveland, CO, 80538, United States
Crisp morning air and a summer sunrise in Colorado. YES PLEASE! Join us on the foothills at Lory State Park for a fun & beautiful morning trail race experience.
This run race features three distances (a 10 mile, a 5 mile and a 5K) that are great for just about any level athlete at any age. Run on a beautiful & scenic course among the treetops with views of Horsetooth reservoir, Fort Collins & the foothills. Bring the kiddos too as the 5K route is very beginner friendly.

Boulder Sunrise Triathlon
2026-06-28 | Boulder Reservoir, 5275 Reservoir Road, Boulder, CO, 80301, United States
Kick off your summer of racing in Boulder.

The Blue Sky Ascent
2026-06-28 | Idaho Springs, Idaho Springs, United States
Although the air will be noticeably thin at the starting line, Echo Lake’s 10,600 feet of elevation is just the beginning. The climb totals nearly 4,000 vertical feet – much of it above treeline – as you make your way 14.5 miles to the finish line located at the summit of one of the most recognizable peaks on Denver’s mountain skyline – 14,264 foot Mt. Blue Sky.
Be inspired!!!
Join us for another memorable run. Spectators will include Bighorn Sheep, Marmots, and Mountain Goats – maybe even a few people!!!

Boulder Rez Marathon
2026-08-15 | Boulder Reservoir, 5275 Reservoir Road, Boulder, CO, 80301, United States
This amazing run course will take you alongside the Boulder Reservoir, remaining mostly on dirt roads and trails. The course is flat with only 200 feet of gain, and will provide views of the Boulder Reservoir and Rocky Mountains.

Boulder Sunset Triathlon
2026-08-29 | Boulder Reservoir, 5275 Reservoir Road, Boulder, CO, 80301, United States
Join us for an unforgettable morning at the Boulder Reservoir. Although this race does not take place at sunset, it will take place at the end of the summer– it’s sister race is the Boulder Sunrise in June. Experience gorgeous views at the recently upgraded venue. All participants receive stellar race shirts and finisher medals, too. This race is a favorite for beginners due to the flat bike course and a packed dirt trail run course.

Narrowleaf Lake Run
2026-10-31 | Boyd Lake State Park (Loveland), 3720 N County Road 11-C, Loveland, CO, 80538, United States
Brisk autumn running in Colorado – OH YEA! Join us for a family fun event with FIVE distance options at the beautiful Boyd Lake State Park venue.
Choose your adventure! Heavy 5K, 10K, 15K (4, 7 or 10 mile) or 1 Mile Pumpkin race options. There is also a Kid’s Fun Run (1 & 1/2 mile options) as well!
This course is on perfectly paved walkways with about a half mile being off road on the south loop. Beautiful lake and wildlife views, NO vehicle traffic to worry about and fun post race festivities. Did we mention almost no elevation gain? This is one flat course making sure you’ll set a new PR or enjoy a fun steady-paced morning run race.
What’s a “Narrowleaf”?? The Narrowleaf Cottonwood Trees are the most densely populated tree species at Boyd Lake State park. We thought the name was fitting and unique to this venue.
