Discover the O'Brien Trail Races, a cornerstone event in the Minnesota trail running scene, set to challenge and delight runners on Saturday, September 26, 2026. Nestled in the scenic William O'Brien State Park in Marine on St. Croix, MN, this race weekend offers a range of distances to suit every trail enthusiast, including a 50K, 25K, 10K, and 5K. The courses weave through beautiful landscapes, primarily on groomed dirt roads and wide grass trails, featuring rolling hills and several notable climbs within the park's upper section, south section, and Jackson Meadows. Expect approximately 95% unpaved trails, offering a true trail running experience with typical race day conditions in late September presenting highs around 70°F and lows near 47°F, with a low chance of precipitation.

The O'Brien Trail Races are renowned for their accessible and welcoming atmosphere. For those new to trail running or seeking a fun, family-friendly event, the 5K and 10K races offer a fantastic introduction, utilizing wide grass trails that include one significant hill and a flat finish. More seasoned trail runners tackling the 25K and 50K distances will find a rewarding challenge on trails described as "very runnable" with "plentiful aid stations" to support their efforts. The 50K, run as two 25K loops, includes four aid stations per loop stocked with water, sports drinks, cookies, and other snacks, with drop bag access at the start/finish area.

All races commence and conclude at the William O'Brien State Park Visitor Center, where runners will find convenient parking and restroom facilities. This event, first established in 2011, is a highlight of the Minnesota Trail Series, known for its well-organized execution and the stunning natural beauty of the St. Croix Valley. Optional race shirts are offered to keep entry fees low, emphasizing the event's commitment to making trail running accessible to all.