Summit Line
Start free

Training for Dinosaur Valley Endurance Run?Build your plan free →

⏵ Course guide · Texas ultra

Dinosaur Valley Endurance Run Course Guide

The Dinosaur Valley Endurance Run is a loop ultra at Dinosaur Valley State Park in Glen Rose, Texas, stacking a 10.5-mile main loop again and again across five distances, from a 5 Mile up to the 100. It does not look like much on paper, rolling ground through open fields and cedar woods, but the climbing adds up fast and the repetition tests you as much as the terrain does. This race ran for years in Dallas as the Big Cedar Endurance Run before moving to Glen Rose and taking the Dinosaur Valley name. I will walk you through the loop first, then give you a pacing and fueling plan built for the repetition and the rolling ground. There are free calculators along the way to dial in your own numbers.

⏵ At a glance

Dinosaur Valley Endurance Run quick facts

Date
November 21 to 22, 2026; confirm the current year with the race
Location
Dinosaur Valley State Park, Glen Rose, TX, outside the Dallas-Fort Worth metroplex
Distances
100 Mile · 100K · 50K · 25K · 5 Mile
Elevation gain
Roughly 9,000 ft for the 100 Mile, 5,700 ft for the 100K, 2,900 ft for the 50K, 1,400 ft for the 25K, and 400 ft for the 5 Mile (all approximate gain and loss, per the race)
Start
100 Mile and 100K start 7 AM Saturday; 50K and the first 25K/5 Mile heat start 8 AM Saturday; a night 5 Mile goes off 8 PM Saturday, and a second 25K/5 Mile heat starts 8 AM Sunday
Cutoff
Rolling Sunday cutoffs close at 5 PM for every distance, about 34 hours for the 100 Mile from its Saturday 7 AM start; 28 aid stations on the 100-mile course
Qualifier
Western States 100 qualifier: the 100K under 22 hours or the 100 Mile under 35 hours

These facts come from the race's own site. Check the current date, start times, cutoffs, and aid stations in the race-day details before you commit. Race logistics change year to year.

The course: where Dinosaur Valley is won and lost

Dinosaur Valley is a loop race built from two loops: a 10.5-mile main loop and a shorter 5-mile loop, both through Dinosaur Valley State Park outside the Dallas-Fort Worth metroplex. The 5 Mile runs the short loop once. The 25K adds one lap of the main loop onto the short loop. The 50K runs the main loop three times, the 100K six times, and the 100 Mile nine times before finishing with the 5-mile loop. No single climb defines the course, just constant rolling across open fields and wooded escarpment, and the gain quietly stacks up to around 9,000 feet by the time a 100-mile runner is done.

The loop math: how the distances stack up

Every distance here is built from the same two loops, so the race really comes down to how many times you repeat them. The 5 Mile is the short loop by itself. The 25K opens with the short loop, then adds one lap of the 10.5-mile main loop. The 50K is three laps of the main loop, the 100K is six (100-mile runners get a recorded 100K split right here, at the end of lap six), and the 100 Mile keeps going for three more laps of the main loop before closing with the 5-mile loop.

Knowing that math before race day matters. If you have just finished lap one of nine in the 100, you still have eight main loops and the closing five-miler ahead of you, and it helps to think in laps rather than miles once the day gets long.

The footing: fields, woods, and everything between

The trail moves between open double-track through fields and single-track through cedar and hardwood forest, with a mix of packed dirt, small rocks, larger rocks, slickrock, and some roots. None of the climbing is steep, but the surface changes constantly, so you are always adjusting your stride. There are no river crossings on the current course, the race dropped them starting in 2018, so what you get instead is honest rolling terrain and a handful of overlooks where you can see for miles.

Slickrock lives up to its name when it rains, so watch your footing on wet sections and shorten your stride on anything technical, especially late in the race when your legs are tired and it is dark.

The night and the repetition (the 100 and the 100K)

The 100 Mile starts at 7 AM Saturday and runs through the night, so you will cover at least one full loop, likely more, in the dark on rolling ground. Carry a real headlamp with a backup, dress for a night that can drop toward 40 degrees, and expect your pace to slow on the technical stretches after dark. The 100K starts alongside the 100 Mile at 7 AM and, depending on your pace, may also see some night miles.

The bigger challenge by lap six or seven is mental. You have already seen every field crossing and every stretch of woods more than once, so break the race into laps, not miles, and give yourself something to look forward to at each pass through the start/finish.

Aid, crew, and the long-day math

There are 28 aid station stops across the 100-mile course, so help is rarely far away, and the loop format means your crew can set up once at the start/finish and see you every lap. Still, carry enough fluid and calories to cover the longer gaps comfortably instead of running in empty.

The race runs a series of rolling Sunday cutoffs rather than one flat number. The 100 Mile has to be through the mile-84 aid station by 12:30 PM Sunday, out of the mile-92 aid station by 3 PM, and starting the closing 5-mile loop by 4 PM, with a final cutoff of 5 PM Sunday for every distance still on course. Starting at 7 AM Saturday, that works out to about 34 hours for the 100 Mile, generous but not unlimited, so stage your gear by lap and keep your stops short.

Pacing strategy for a rolling, repeated loop

Dinosaur Valley is not a course you pace off a flat-ground split chart. The constant rolling, the mixed footing, and the lap-after-lap repetition mean you manage effort and discipline, not a number on your watch. Run the first loop like you still have most of the day, and maybe the night, ahead of you, because in the longer distances here you do.

Pace by effort and grade, not by the watch

Your flat road pace does not translate to this rolling, mixed-surface course. What matters is the effort you can hold lap after lap and the time the terrain actually costs you. Run the runnable rollers, hike the steeper punches without guilt, and keep your output even instead of surging every little rise. Use a grade-adjusted pace to turn your real fitness into honest targets on ground like this, and you will not torch your early laps and pay for it late.

Build a loop-aware finish prediction

Do not guess your Dinosaur Valley finish off a road time. The rolling gain and the night miles on the longer distances all add real time, and the smart move is to plan per lap. Build a finish prediction that accounts for this course’s rolling terrain, then divide it into target lap splits with honest slow-down baked into the later laps. Knowing your planned time per loop lets you check yourself at the start/finish each lap and see how much cushion you have against the rolling cutoffs, instead of guessing in the dark.

⏵ Free tools to pace this course

Fueling strategy for a long loop day

A 5 Mile or 25K here is over in a morning, the 50K and 100K are most of a day, and the 100 Mile is an all-day-and-night effort that can stretch past 30 hours. Over that range, the runners who keep eating and drinking are the ones still moving at the end, so carbohydrate, sodium, and fluid matter as much as fitness.

Carbs: steady, trained, and easy to take every lap

Aim for around 60 to 90 grams of carbohydrate per hour, and only push the high end if your gut is trained for it. The loop format actually helps: you can restock real food and your own fuel at the start/finish every lap, so build a plan you can repeat without thinking. The trap on a long day is letting your stomach quit because you got behind early, so keep your intake steady and easy to get down from the first loop instead of trying to claw calories back deep into the night. Practice your exact race-day carb rate on long runs so it feels routine, not like an experiment.

Sodium and fluid: cover the gaps and the swing in weather

Late November in Glen Rose can run warm and humid or cool and damp, with a typical low near 40 and a high near 69, so set your sodium to the day: often somewhere around 400 to 700 milligrams per liter of fluid, higher if it is warm or you are a salty, heavy sweater. Aid stations come around often across the loop, 28 stops on the 100-mile course, so you are rarely far from a refill, but weigh yourself before and after a long run in similar conditions to find your real sweat rate and build the plan around your own number rather than a generic guess.

⏵ Build your fueling plan

Get a carb, sodium, fluid, and caffeine plan per hour built for your weight, your goal time, and the Dinosaur Valley conditions 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 Dinosaur Valley loop profile, and your projected per-lap splits. Summit Line reads your real training, builds a plan for the rolling terrain and the repetition, and rehearses your fueling so race day is something you execute, not guess at.

Start free →Explore the demo

Dinosaur Valley Endurance Run FAQ

How hard is the Dinosaur Valley Endurance Run?

Harder than the flat-looking Texas map suggests. The course rolls through Dinosaur Valley State Park on a mix of double-track through open fields and single-track through cedar and hardwood, with packed dirt, rocks, slickrock, and some roots underfoot. The 100 Mile stacks nine laps of the 10.5-mile main loop plus a closing 5-mile loop, so a big part of the difficulty is repeating the same rolling ground long after your legs are tired, not any one climb. The footing punishes careless feet, especially at night, so this is a race about staying steady and paying attention, not raw speed.

How much climbing is in the Dinosaur Valley Endurance Run?

It adds up fast because the trail rolls the whole way. The race lists roughly 9,000 feet of combined gain and loss for the 100 Mile, 5,700 feet for the 100K, 2,900 feet for the 50K, 1,400 feet for the 25K, and 400 feet for the 5 Mile. None of it is one big mountain. It is short, repeated rollers, and stacking laps for the longer distances is what turns that into real vertical over the course of a day.

What is the loop format at Dinosaur Valley?

Everything is built from a 10.5-mile main loop plus a shorter 5-mile loop. The 5 Mile is that short loop on its own. The 25K runs the 5-mile loop, then adds one lap of the main loop. The 50K is three laps of the main loop, the 100K is six, and the 100 Mile is nine laps of the main loop followed by the 5-mile loop to close it out (100-mile runners also get a recorded 100K split at the end of lap six). Because you pass the start/finish area on every loop, crew access and drop bags are easy, and the terrain gets familiar fast, for better and worse.

What are the cutoff times for the Dinosaur Valley Endurance Run?

The race runs a series of rolling cutoffs through Sunday rather than one flat number. The last incremental cutoff for every distance is 5 PM Sunday, and the 100 Mile has checkpoints along the way (through the mile-84 aid station by 12:30 PM Sunday, out of the mile-92 aid station by 3 PM, starting the last 5-mile loop by 4 PM). Starting at 7 AM Saturday, that gives 100-mile runners about 34 hours total. Always confirm the exact schedule and cutoff times in the current race-day details, since aid station names and mile markers can shift year to year.

What is the terrain and weather like at Dinosaur Valley?

The course mixes open double-track through fields with single-track through cedar and hardwood forest, on packed dirt, small rocks, larger rocks, slickrock, and some roots. There are no river crossings on the current course (the race dropped them starting in 2018). Late November in Glen Rose runs a low near 40 and a high near 69 degrees, with a modest chance of rain, and the 100-mile field runs through a full night on the trail, so pack for cold and dark. Watch your footing on the slickrock when it is wet, and know that copperheads, bobcats, and coyotes live in these woods even if they rarely cause trouble.

Is the Dinosaur Valley Endurance Run a good first 100 (or first ultra)?

It is a reasonable 100-mile debut and a solid choice for a first ultra at the 5 Mile, 25K, or 50K distance. The loop format keeps aid and crew close by on every lap, the shorter distances give you an easy entry point into the same course, and the roughly 34-hour cutoff for the 100 Mile is forgiving if you have built the durability for the terrain. What it asks for is comfort on rolling, mixed footing and the patience to repeat that ground lap after lap, so train on similar terrain and rehearse running tired before you toe the line.

This guide is independent and for planning only. The course details, dates, start times, 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.

⏵ Your race day, computed

Projected splitsYour split sheet for Dinosaur Valley Endurance Run, built from your own runs at matching grades, not a flat-course calculator.
See yours free →14 days of everything · no card

The timeline

Get the week-by-week countdown for this race: when to build, when to peak, when to taper.

One email with the timeline, plus training notes for this race. Unsubscribe any time.