calendar_today 29 Mar, 2026 – 11 Apr, 2026
directions_run Running
language Official Website
sell $20.00 – $55.00
RMRR provides low-cost, low-keyed, supported, and timed training races for runners of all abilities. The races are planned to help you prepare for Boston, Colorado, Colfax, and other long spring races. We make it easy for you to work on your pace, your nutrition and drinking, and getting everything ready for your big race.
Sign up for one, or save money and choose the two race bundle. RMRR members get 50% off.
The races begin at 8am, at the Platte River Trailhead Park, at 88th and Colorado, in Thornton. The courses are out-n-back. so we can accommodate almost any distance between 10-20 miles.
Please note that for everyone's safety dogs or running strollers are not permitted on our courses. Thanks for understanding.
Mar 29, 2026
Distance — 10 Miles
Type — Running
08:00
$20.00
Mar 29, 2026
Distance — 40 Miles
Type — Running
08:00
$55.00
Mar 29, 2026
Distance — 20 Miles
Type — Running
08:00
$30.00
Mar 29, 2026
Distance — 20 Miles
Type — Running
08:00
$35.00
These values represent the 3-year monthly averages for March in Thornton.
Learn more about the host city, Thornton.
Thornton is a city of about 144,000 in the Denver Metropolitan Area of the western U.S. state of Colorado. The city lies northwest of Denver in Adams and Weld counties. It is a diverse community with a strong commitment to quality of life and environmental issues.
Read more launchRead what other athletes have to say about their experience at the RMRR Spring Marathon Training Series #1.
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