⏵ Course guide · Mid-Atlantic 50-miler
Stone Mill sends its field across the Seneca Greenway and Muddy Branch trails in Montgomery County, Maryland, roughly 4,000 feet of climbing over 50 rolling, forested miles, against a strict 13-hour cutoff. A club-run staple of the Montgomery County Road Runners Club. I will walk you through the course and cutoffs first, then give you a pacing and fueling plan built for a permit-strict finish window, plus free tools to dial in your own numbers.
These facts come from the official Stone Mill 50 race site. Check the current year details, cutoffs, and aid stations before you commit. Race logistics change year to year.
Stone Mill runs a point-to-point-feeling out-and-back style route across the Seneca Greenway and Muddy Branch trail networks, forested and rolling, on primarily single-track dirt trail.
The course traverses forested, rolling terrain with small stream crossings along the way. Most of it drains well, but the organizers are upfront that parts can turn muddy in wet weather. A rainy week before race day can meaningfully change footing, so check conditions in the days leading up if the forecast has been wet.
Nine aid stations dot the course, eight full stops plus one water-only station, spaced roughly 4 to 6 miles apart. Bag drops sit at Pennyfield Lock (mile 24.3) and Riffle Ford Road (mile 42), giving you two real chances to swap gear or restock beyond what you carry.
The official elevation profile lists about 4,000 feet of total gain over 50 miles, a moderate number by ultra standards. It is not one defining climb, it is continuous rolling terrain, which means there is rarely a long stretch to fully recover your legs, even without a single big mountain to point to.
The 13-hour cutoff at Stone Mill is not a soft target. It is tied to the park permit and gets strictly enforced, so build your pacing plan around the intermediate checkpoints, not just the finish line.
Stone Mill publishes cutoffs at every major aid station along the way, giving you real checkpoints roughly every 5 to 8 miles. A grade-adjusted pace target for the rolling, forested terrain, checked against those published times, tells you early whether you have real margin or need to tighten your effort well before the final miles.
Continuous rolling terrain rarely lets you make up lost time late in an ultra. A vert-aware finish prediction built off your early-race splits, run against the strict 7:00 PM close, gives you an honest read on whether your current pace holds, well before you are fighting the clock in the final aid stations.
⏵ Free tools to pace this course
A 6:00 AM start in November means a cold opening stretch, warming through midday, then cooling again as you approach the evening cutoff.
Aim for roughly 60 to 90 grams of carbohydrate per hour. With eight full aid stations plus a water-only stop spread roughly 4 to 6 miles apart, and bag drops at Pennyfield Lock and Riffle Ford Road, you have plenty of chances to keep your intake on schedule instead of front-loading or skipping stretches.
Start conservatively, 300 to 500 mg of sodium per liter, in the cold early miles, and move toward 500 to 700 mg per liter as the day warms and your effort accumulates over 50 miles. Small stream crossings mean wet feet are part of the day, so plan a dry sock change at one of your bag drops if that helps you stay comfortable and moving.
⏵ Build your fueling plan
Get a carb, sodium, fluid, and caffeine plan per hour built for your weight, your goal time, and a cool November day in Maryland 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 Stone Mill elevation profile, and your projected splits. Summit Line reads your real training, builds a plan for a strict cutoff, and rehearses your fueling so race day is something you execute, not guess at.
Stone Mill is a moderate, runnable 50-miler by ultra standards, roughly 4,000 feet of total gain on forested, rolling single-track through the Seneca Greenway and Muddy Branch trails, but the strict 13-hour cutoff, enforced to the minute due to park permit requirements, is what makes this one honest. It is a club-run race by the Montgomery County Road Runners Club and a common first-50-mile choice for Mid-Atlantic runners, with intermediate cutoffs at every major aid station to keep you honest along the way.
The official course page lists roughly 4,000 feet of total elevation gain over the 50 miles, spread across forested, rolling terrain on primarily single-track dirt trail. That works out to a modest per-mile grade compared to mountain ultras, but small stream crossings and sections that turn muddy in wet weather add real effort the elevation number alone does not capture.
A November race in Maryland typically means cool morning temperatures at the 6:00 AM start, warming through midday before cooling again toward the 7:00 PM cutoff. Aim for roughly 60 to 90 grams of carbohydrate per hour, and keep sodium in the 300 to 700 mg per liter range. With 8 full aid stations spaced roughly 4 to 6 miles apart, you have frequent chances to reset your intake rather than carrying huge reserves between stops. Build your numbers with the free ultra fueling calculator before race day.
The overall cutoff is 13 hours, or 7:00 PM from the 6:00 AM SHARP start, strictly enforced because of park permit requirements. The race also runs intermediate cutoffs at major aid stations along the way (roughly 6.5 hours to Pennyfield at mile 24.3, 10 hours to Route 28 West at mile 34.3, and just over 12 hours to Route 355 near the finish), so you get real checkpoints to gauge your pace rather than a single finish-line deadline.
The course runs on the Seneca Greenway and Muddy Branch trails in Montgomery County, forested and rolling, primarily single-track dirt trail with small stream crossings. Most of the course drains well, but sections can turn muddy in wet weather, so November rain in the days before the race can change footing conditions materially.
Stone Mill is a well-regarded first-50-mile choice in the Mid-Atlantic: the terrain is rolling rather than mountainous, the course is dense with 8 full aid stations, and the club-run field (Montgomery County Road Runners Club) has decades of experience supporting new ultra runners. The one thing to respect is the strict, permit-driven 13-hour cutoff. It will not bend, so build a real pacing plan against the intermediate checkpoints rather than assuming you can make up time late.
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<a href="https://runsummitline.com/guides/stone-mill-50">The Stone Mill 50 Mile Run course guide</a><iframe src="https://runsummitline.com/embed/race/stone-mill-50" style="width:100%;max-width:420px;height:180px;border:0;" loading="lazy" title="Stone Mill 50 Mile 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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