⏵ Course guide · Flint Hills, Kansas
The Heartland 100 runs out and back on backcountry gravel roads through the Flint Hills tallgrass prairie near Cassoday, Kansas, roughly 6,000 feet of climb on the 100-mile course and 22 aid stations along the way. I will walk you through the aid station layout and cutoffs first, then give you a pacing and fueling plan built for exposed prairie gravel, plus free tools to dial in your own numbers.
These facts come from the official UltraSignup registration page. Check the current year details, aid stations, and cutoffs before you commit; race logistics can change year to year.
The historic Heartland 100 course runs out and back on backcountry gravel and dirt roads with less than a mile of pavement, through open-range Flint Hills tallgrass prairie with stunning, exposed views and almost no shelter.
The 100-mile course carries 22 total aid stations, roughly every 4 to 6 miles, with 9 offering crew access and 14 usable for drop bags. Crew vehicles are restricted to designated access roads; study the official crew-directions map if you are bringing support, since driving the course itself during the race is not allowed except at those specific points.
Runners who choose the 125 Mile take on the historic Heartland course plus a 30-mile detour loop out to Eureka, Kansas, with minimal course marking and turn-by-turn directions provided in advance. Race organizers are explicit that this is a "graduate level" option requiring real navigation skill, not just extra fitness.
Much of the course crosses open range with grazing cattle. The official guidance is clear: remain calm and walk through a herd if you encounter one, since running or shouting can cause the animals to scatter unpredictably into your path.
The 14-hour cutoff to reach the 50-mile turnaround is tighter than the remaining 16 hours you get for the return trip, so the race\'s own FAQ is direct: if you cannot reach 50 miles in 14 hours, the second half in 16 is unlikely too.
A grade-adjusted pace target for the rolling gravel and open prairie gives you an honest number for the outbound half, and hitting the 50-mile turnaround with real margin before the 14-hour cutoff protects the rest of your day. Pacers are only allowed starting at Matfield Green (mile 42.5 for the 100 miler), so plan your solo pacing discipline for everything before that point.
⏵ Free tools to pace this course
October is chosen to minimize Kansas weather extremes, but a normal high near 70 can still swing to a record 89, and normal lows near 44 can drop to a record 30, with almost no shelter on course.
Aim for roughly 60 to 90 grams of carbohydrate per hour, and keep sodium in the 300 to 700 mg per liter range, adjusting up if the day runs warm. With 22 aid stations spread across the course, you have frequent chances to reset, but the open, exposed prairie means wind and sun exposure between stations matter more here than on a shaded trail course.
⏵ Build your fueling plan
Get a carb, sodium, fluid, and caffeine plan per hour built for your weight and your goal time with the free ultra fueling calculator. Browse the rest of the free running tools at the tools hub.
⏵ Train for it with Summit Line
Get a race-day plan built around YOUR fitness, this out-and- back Flint Hills course, and your projected splits. Summit Line reads your real training, builds a plan for open, exposed gravel miles, and rehearses your fueling so race day is something you execute, not guess at.
Heartland 100 is an out-and-back race on backcountry gravel roads through the Flint Hills tallgrass prairie near Cassoday, Kansas, with roughly 6,000 feet of climb on the 100-mile course and less than a mile of pavement. It is a required leg of the Kansas Grand Slam of Ultrarunning, which tells you how the local ultra community rates it. The difficulty is not technical footing, it is exposure: open range with little shelter, real Kansas weather swings (record highs near 90, record lows in the upper 20s in October), and rolling gravel miles that add up.
The full lineup is the 125 Mile (a "graduate level" course with a 30-mile detour loop and minimal marking), the 100 Mile, the standard 100K, the Teter Rock 100K (an out-and-back detour to Teter Rock), the 50 Mile, the Cassoday Marathon, and the Teter Rock Half Marathon, plus a new 4-person, 100-mile relay for 2026. Most of the shorter distances are out-and-back segments of the historic Heartland 100 course, so even the marathon and half marathon runners experience the same gravel-road terrain as the ultra field.
The 100-mile course has 22 total aid stations, 9 with crew access and 14 usable for drop bags, spaced roughly every 4 to 6 miles with clear cutoff times posted at each. Crew vehicles are not allowed on the course except at designated crew-access points, and specific rules apply, for example, runners must physically check in at Ridgeline aid station rather than yelling from the road. Study the aid station list and crew-access map before race day if you plan to have support meet you along the way.
October in Kansas is chosen specifically to minimize weather extremes compared to summer, but conditions can still swing from a warm afternoon (record high 89) to a cold night (record low 30), and this is open prairie with almost no shelter from wind or storms. Aim for roughly 60 to 90 grams of carbohydrate per hour, and keep sodium in the 300 to 700 mg per liter range, adjusting for the day's actual conditions. With aid roughly every 4 to 6 miles, use that frequency to stay consistent rather than carrying large reserves. Build your numbers with the free ultra fueling calculator before race day.
The 100 Mile and 100K share a 30-hour overall cutoff, with a 14-hour cutoff to reach the 50-mile turnaround (versus a full 16 hours for the second half, since the outbound trip is generally the faster half). The 50 Mile has a 15-hour cutoff with a 7-hour cutoff at its 25-mile turnaround. The Marathon cutoff is 10 hours, and the 125 Mile gets 38 hours. These cutoffs apply equally regardless of which early-start option you use, so know your real numbers before choosing an early start.
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<a href="https://runsummitline.com/guides/heartland-100">The Heartland 100 course guide</a><iframe src="https://runsummitline.com/embed/race/heartland-100" style="width:100%;max-width:420px;height:180px;border:0;" loading="lazy" title="Heartland 100 course guide by Summit Line"></iframe>This guide is independent and for planning only. The course details, dates, cutoffs, and aid stations come from public sources and can change year to year, so confirm the current specifics with the official race before you register or run. The fueling and pacing advice is general and not medical advice.