Explore the Cap Sauers Holding Nature Preserve - the largest tract of undeveloped land in Cook County, IL. This race will cover every inch of maintained trail within the Nature Preserve. With over 1000 ft of elevation, this marathon is mountainous by Chicago standards!
The course uses the Sag Valley Trail system, covering the Yellow, Green, Blue & Tan trails. The whole course is wide horsetrail, allowing for 2-way traffic and encouragement from fellow participants. 
Results here:  https://sites.chronotrack.com/event/92163/results
2026 Photos here:  https://www.flashframe.io/search/2861/
2025 Photos here:  https://www.highfivebb.com/Running/F3-Cap-Sauers-Trail-Marathon-10-Mile-May-10-2025