The Underdown Trail Races are grassroots trail runs in northern Wisconsin. It offers runners a wilderness experience on challenging trails formed by glaciers that swept the area thousands of years ago. The course is primarily singletrack, climbing hills (up to 70!) that pass by isolated lakes and dozens of boardwalks.
For more races, check out our Running Races Calendar across the US.
Contents
Race Info
The race will be held concurrently with the Thunderdown in the Underdown Wisconsin Endurance Mountain Biking Series (WEMS) races.
This is a challenging trail run on challenging terrain that goes through some remote areas. If you have not trail run before, we recommend signing up for one of our shorter races first. Finish it, and you just might burst with pride and happiness.
Each distance is limited to 100 runners to provide an intimate trail experience for each runner. As part of that experience, you will get a well-marked, custom, commemorative Underdown pint glass, awards for finishers, stocked aid stations, and drop bag transport. After the race, you should join the party with live music from The Northwoods Skitchers, food, beer, and other goodies.
Race Date
August 16, 2025.
Location
Prairie Dells Trail Head,
Merrill, WI 54452 US
Directions
Distances
- 60K
- Marathon (26.2 miles)
- Half marathon (13.1 miles)
Starting Time
- 9:30 AM – 60K
- 10:15 AM – full marathon
- 11:30 AM – half marathon
Entry Fees
- $65 and up – 60K
- $50 and up – full marathon
- $40 and up – half marathon
Course Map
You can find the course map and description here: ironbull.org.
Registration
To participate in the Underdown Trail Race, register here ironbull.org.
Official Race Website
Always refer to the official website for the latest race information: ironbull.org.
Social Media
If you are looking for more information about the race, follow it on Facebook, Twitter and Instagram.
Related Events
If you’re looking for more races like this, have a look at our Ultra Marathons Calendar. You may also like to participate in other races in August.
More races in Wisconsin: 5K, 10K, Half Marathons, Marathons, Ultra Marathons, 50K, 50M, 100K, 100M
