Montgomery Village, USA ·
Nov 7, 2026
50 miles of rolling forest singletrack on the Seneca Greenway and Muddy Branch trails, in the heart of Montgomery County, Maryland
The Stone Mill 50 Mile Run is a trail ultramarathon organised by the Montgomery County Road Runners Club (MCRRC) in Montgomery Village, Maryland. Starting and finishing at Stedwick Elementary School, it covers 80 km of mostly single track through the forests of the Seneca Greenway and Muddy Branch trails, with around 1,200 m of climbing and a strict 13 hour cutoff.
Every November, the Stone Mill 50 Mile Run sends runners out at 6:00 AM sharp from the parking lot of Stedwick Elementary School in Montgomery Village, Maryland. Organised by the Montgomery County Road Runners Club, the race covers 50 miles (80 km) of forested, rolling terrain on the Seneca Greenway and Muddy Branch trails, for roughly 1,200 m (4,000 ft) of total climbing. The 2026 edition takes place on Saturday 7 November.
The course is primarily dirt single track, with small stream crossings and sections that can turn muddy in wet weather, although most of it drains well. It heads south through the woods to Blockhouse Point Conservation Park near Potomac and the Stone Mill aid station at mile 27.8, then swings back north via Route 28 and Riffle Ford Road, where runners pass several stations for a second time before returning to Montgomery Village. White flags bearing the Stone Mill logo and yellow ribbons mark the way, and drop bags wait at Blockhouse Point and Riffle Ford.
Stone Mill is known for its amazing aid stations: nine of them, each run by its own dedicated volunteers with different food on the table, plus water and Tailwind. It is a true club race, where entrants pledge six hours of volunteering before race day and where 5, 10 and 15 year finishers are celebrated. The 13 hour limit, set by the park permits, is strictly enforced: everyone must be home by 7:00 PM.