MammothMarch Missouri

The MammothMarch Missouri returns to Defiance, Missouri on September 13th, 2026. The event is held at the remote Weldon Spring Conservation Area in western Missouri, just a half-hour west of St. Louis. This year's edition features a challenging single-circuit hiking loop that covers an impressive 20 miles along diverse trails, including parts of Katy Trail and Lewis & Clark Trail.
Race morning finds participants assembling under clear skies at Defiance Ridge Vineyards, the picturesque start and finish point for this mammoth trek. The atmosphere is one of anticipation as runners prepare to tackle the long distance across varied terrain. This event has been a staple in Missouri's outdoor calendar since its inception, drawing enthusiastic hikers from far and wide.
The race route offers breathtaking views of the Missouri River, making every step memorable. Participants will hike through different sections of the conservation area, each offering unique vistas and challenges. The 20-mile journey is both demanding and rewarding, pushing participants to their limits while also immersing them in nature's beauty.
Course and conditions take center stage on this autumn morning. The trail surface varies from rocky paths to well-defined dirt trails, providing a mix of surfaces that test endurance. The race will follow a single loop starting and finishing at Defiance Ridge Vineyards, ensuring participants experience the full scope of the conservation area. Aid stations are strategically placed along the route for hydration and rest.
Weather on September 13th can be expected to range from cool mornings to warmer afternoons. Temperatures will average around 22°C with a minimum of 16.7°C, making it comfortable but not too warm for an extended outdoor activity. The humidity levels at about 70.8% mean participants should dress in layers and stay hydrated throughout the event.