⏵ Course guide · North Texas classic since 1999
The Grasslands Trail Run has run at the LBJ National Grasslands near Decatur since 1999, five distances from a 15K to a full 100 mile on roughly 45 miles of unique rolling trail. I will walk you through the loop structure and intermediate cutoffs first, then give you a pacing and fueling plan built for this gentle but long North Texas course, plus free tools to dial in your own numbers.
These facts come from the official Blaze Trails Running race-details page. Check the current year details, cutoffs, and aid stations before you commit. Race logistics change year to year.
All distances run out of TADRA Point on the LBJ National Grasslands' Blue, White, Yellow, and Red trails, with the Marathon, Half Marathon, and 15K each covering 100% unique trail rather than sharing sections with the ultra distances.
With about 4,000 feet of gain across the full 100 miles, this is a low vert-per-mile course through rolling hills, pine and oak forest, and open grassland. The official page recommends it as an excellent choice for a first trail race at any distance, precisely because the terrain itself is not the main obstacle: distance and time management are.
The Grasslands has roughly 45 miles of non-overlapping trail, and the course shares the land with grazing cattle leased by the Forest Service. Runners are asked to close and chain cattle gates behind them and give any cows on the trail plenty of room: an unusual but genuine part of the course experience here.
The 100 mile is broken into named loop starts with hard deadlines: the second Blue Loop (mile 54.9) by 9:30 PM Saturday, past the Red Ant aid station (mile 66.4) by 1:30 AM, the final Red Loop (mile 82.5) by 5:45 AM Sunday, and the final Yellow Loop (mile 91.4) by 8:15 AM Sunday, ahead of the 11 AM overall finish deadline. A full pace chart for 20, 24, and 30 hour finishes is published on the official site.
With a runnable profile and clearly staged intermediate cutoffs, the 100 mile here rewards steady, sustainable pacing more than raw climbing strength.
Blaze Trails publishes a full pace chart for 20, 24, and 30 hour 100 mile finishes. Start there, then build your own race-time calculator projection so you have a personal target for each of the four named loop-start deadlines rather than relying on someone else's generic pace band.
Even with a gentle profile, a grade-adjusted pace target keeps your effort honest across rolling hills that add up over 100 miles. The relatively low vert here can tempt runners into starting too fast; treat the gentle terrain as a reason to run efficiently, not a reason to skip pacing discipline.
⏵ Free tools to pace this course
A 5 AM Saturday start on the 100 mile means potentially two nights on course for the slower end of the field, so plan your calories and warm layers for real overnight running.
Aim for roughly 60 to 90 grams of carbohydrate per hour. Daytime aid stocks bananas, oranges, potato chips, Oreos, fig cookies, applesauce, PB&Js, peanut butter cookies, and fruit snacks, and hot food service kicks in overnight with ramen, mashed potatoes, quesadillas with cheese, and vegan options like avocado or bean dip, plus hash browns and bacon at some stations.
Sodium in the 300 to 700 mg per liter range covers most runners in typical mid-March North Texas weather, which can range from cool nights to mild days. SaltStick and ginger candies (for nausea) are available at every aid station as a backup to your own plan.
⏵ Build your fueling plan
Get a carb, sodium, fluid, and caffeine plan per hour built for your weight, your goal time, and a March North Texas day and night 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 exact gentle-but-long grassland course profile, and your projected loop-deadline splits. Summit Line reads your real training, builds a plan for a runnable multi-loop 100, and rehearses your fueling so race day is something you execute, not guess at.
Official race copy describes a "gentle elevation profile" (roughly 4,000 feet of gain on the 100 miler) and calls the course "very runnable," making it a good choice for a first trail race at any distance offered. The difficulty on the longer distances comes more from sheer mileage and time on feet than from technical or mountainous terrain: about 45 miles of non-overlapping trail through rolling hills, pine and oak forest, and open grassland.
The official race page states approximately 4,000 feet of elevation gain for the 100 mile distance, on a gentle, runnable profile through rolling North Texas terrain. This is a low vert-per-mile course compared to mountain 100s, which is part of why it is recommended as an approachable first trail race at any distance.
This is a cupless race, so bring your own hydration device. Aid stations stock water (provided by Crazy Water), Gatorade, soda, pickle juice, bananas, oranges, potato chips, Oreos, fig cookies, applesauce, PB&Js, peanut butter cookies, fruit snacks, M&Ms, SaltStick, and ginger candies for nausea. Overnight, hot food service adds ramen, mashed potatoes, quesadillas with cheese, and vegan options like avocado or bean dip. Aim for roughly 60 to 90 grams of carbohydrate per hour on the longer distances, and sodium in the 300 to 700 mg per liter range. Build your own numbers with the free ultra fueling calculator before race day.
The 100 mile has a Sunday 11 AM overall finish deadline, with intermediate deadlines to start each loop: the second Blue Loop (mile 54.9) by 9:30 PM Saturday, past the Red Ant aid station (mile 66.4) by 1:30 AM, the final Red Loop (mile 82.5) by 5:45 AM Sunday, and the final Yellow Loop (mile 91.4) by 8:15 AM Sunday. The 50 mile must finish by 6 AM Sunday, the Marathon and Half Marathon by 11:59 PM Saturday, and the 15K within 3.5 hours (by 11 AM Sunday).
100 mile runners can use a pacer starting at mile 54.9, the start of the blue loop; earlier pacers are by exception only (for example, runners 65+ or those needing help before sunset for vision reasons) and must be requested a week in advance. New for 2027: 50 mile runners can request an exception-only pacer for the final out-and-back section if they will be running it entirely after sunset (around 7:30 PM), by emailing the race at least a week ahead.
Yes, and the organizers say so directly: the gentle, runnable elevation profile and roughly 45 miles of unique, well-marked trail make this "an excellent choice for a first trail race in any distance offered." For a first 100 mile attempt specifically, the Sunday 11 AM cutoff and clearly staged intermediate deadlines give you real structure to pace against rather than a single distant finish clock.
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<a href="https://runsummitline.com/guides/grasslands-trail-run">The Grasslands Trail Run course guide</a><iframe src="https://runsummitline.com/embed/race/grasslands-trail-run" style="width:100%;max-width:420px;height:180px;border:0;" loading="lazy" title="Grasslands Trail Run 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.
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