O'brien Trail Races
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O'Brien Trail Races - William O'Brien State Park, Marine on Saint Croix, MN
The event takes place on Saturday, September 26, 2026, at William O'Brien State Park, 16821 O Brien Trail North. Races use park trails and start at the Visitor Center; parking and restrooms are located at the Visitor Center lot.
Available race distances:
- 50K
- 25k
- 10K
- 5k
The 50K is two 25k loops using the park's upper and south sections and Jackson Meadows. There are four aid stations per loop, drop bags are allowed at the start/finish area only, and the overall finish cutoff is nine hours. Awards are given to the top three men and women in the 50K.
The 25k has four aid stations, a five-hour cutoff, and awards for the top three men and women. The 10K and 5k run on wide grass trails with one large hill and a flat finish; the 10K completes the 5k loop twice. There are no aid stations or awards for the 5k and 10K. All finishers receive a full color 8.5 x 11 print of the current year logo.
Online registration opens on 11/28/2025 and runs through September 21, 2026; race day registration is available at higher fees. Race shirts are offered as an optional add-on. Packet pickup is race morning only. No refunds or transfers; if the event is changed to virtual, race shirts and numbers will be mailed within one week of the completed event. Post-race food and typical aid station items are provided. Respect other park users and use headphones for personal music. Visit the organization's website for the most recent information.
