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Boulder County government offices closed Monday, Oct. 14, in observance of Indigenous Peoples’ Day. The District Attorney’s Office is open Oct. 14.

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October 5, 2023

Boulderthon Race Events in Boulder County on Sunday, Oct. 8, 2023

Residents and Travelers in the Race Areas Should Plan for Detours and Delays


Boulder County, Colo. - The Boulderthon Marathon, Half Marathon, 10K, and 5K races will be held on Sunday, Oct. 8 in Boulder County. Here is what you can expect.

All community members will have access to their homes but may encounter delays and should follow recommended detours. If you are traveling through the area during the event please pay close attention to the Boulder County Sheriff, City of Boulder Police, and traffic marshals to ensure safety for runners and travelers alike.

Road and Trail Impacts

The Marathon, Half Marathon, 10K, and 5K courses will be active between 8 a.m. and 3 p.m. on Sunday, Oct. 8. View an interactive map of the course.

County Closures

  • Valmont Rd. will be closed westbound at Butte Mill Rd. Westbound Valmont Rd. traffic will be diverted south at Butte Mill Rd. to Arapahoe Ave.
  • N 61st St./N. 63rd St. will be closed southbound between Jay Rd. and Valmont Rd. from 7 a.m. to 9:30 a.m. Northbound remains open for local access.
  • N 63rd St. will be closed northbound between Jay Rd. and Spine Rd. from 7 a.m. to 9:30 a.m. Southbound 63rd St. remains open for Notting Hill Gate resident ingress/egress. Twin Lakes residents: Please use Spine Rd. for ingress/egress until 9:30 a.m. and expect delays.
  • Jay Rd. will be closed eastbound between Spine Rd. and 63rd St. from 7 a.m. to 1 p.m.
  • Lookout Rd. will be closed westbound between 75th St. and 95th St. from 7:30 a.m. to noon. Eastbound Lookout Rd. remains open for local access.
  • N 79th St. will be closed northbound between Lookout Rd. and Niwot Rd. from 7:30 a.m. to noon. Southbound 79th St. remains open for local access.
  • N 57th St. will be closed northbound from 7 a.m. to 1 p.m. Residents may access via N 57th. St & Jay Rd., traveling southbound and exiting via Independence Rd. Independence Rd. will be closed eastbound from 7 a.m. to 1 p.m.
  • The following multi-use paths will remain open, but will have heavy runner traffic:
    • Along the west side of 63rd St. between Spine Rd. and Jay Rd. from 9 a.m. to 1 p.m.
    • Along the north side of Niwot Rd. between 79th St. and 95th St. from 8:30 a.m. to 11:30 a.m.

City of Boulder Closures

  • Pearl St. will be closed to all traffic between 15th St. (east end of Pearl St. Mall) and 55th St. from 7 a.m. to 9:30 a.m.
  • Mapleton Ave. will be closed westbound from Folsom St. to 14th St. from 7:30 a.m. to 2:30 p.m.
  • 14th St. will be closed to all traffic between Mapleton Ave. and Pearl St. from 7:30 a.m. to 2:30 p.m. 14th St. will also be closed between Walnut St. and Spruce St. from 6 a.m. on Friday, Oct. 6 through 7:30 p.m. on Sunday, Oct. 8.
  • The following multi-use trails will remain open, but will have heavy runner traffic:
    • Along both sides of Lookout Rd. between Gunpark and 75th St. from 8 a.m. to noon
    • Cottonwood Trail between 47th St. and Independence Rd. from 7:30 a.m. to 1:15 p.m.
    • Wonderland Creek Path between 47th St. and Goose Creek Path from 7:30 a.m. to 1:30 p.m.
    • Goose Creek Path between Folsom St. and Pearl Pkwy. from 7 a.m. to 1:45 p.m.

Information and Event Contacts

If you have questions or concerns, please visit the Boulderthon event website, or email community@boulderthon.org. You may also contact John Holste, Boulder County Special Events Coordinator at jholste@bouldercounty.gov or Justin Greenstein, City of Boulder Special Events Coordinator at greensteinj@bouldercolorado.gov.

CPP Boulderthon 2023 Impact Zones Map


Boulderthon 2023 closure table