C&O Canal 100

The C&O Canal 100 is about as flat as a hundred miles gets. It starts and finishes at Camp Manidokan near Knoxville, Maryland, and almost all of it is run on the towpath of the Chesapeake and Ohio Canal along the Potomac, on packed dirt with small gravel and, the race says, about 60 percent shade. The first loop is roughly 40 miles and takes in an unsupported out-and-back to a turnaround upriver; the next two are about 30 miles each, so runners come back through the camp twice before the finish.

Runners get 30 hours. The race has run since 2013 and has been held on the last weekend of April, and the 2027 edition is on April 24 and 25, starting at 7:00 a.m. on the Saturday. Entry is first-come on UltraSignup, capped at 250, and it sold out by early April in 2026. A finish under the limit is a Western States 100 qualifier.

One loop of about 40 miles and two of about 30, almost entirely on the C&O Canal towpath, starting and finishing at Camp Manidokan. The first loop reaches mile 38.4 and includes a 7.6-mile round trip to the North Turnaround, which has no aid and is a check-in only. The race's mileage table ends at 100.0 miles, and it publishes no climbing figure because there is almost none. Five aid stations (Manidokan, Dargan Bend, Antietam Campground, Keep Tryst and Brunswick) are each passed more than once, and they close at an 18-minute-per-mile pace. Crews can meet runners only at Brunswick and Camp Manidokan, and pacers are allowed from mile 59.6.

Entry is first-come on UltraSignup with no lottery and no qualifying race. For 2027 it opens on January 1 at 10 a.m. Eastern and closes on April 1, the fee is $285 and non-refundable, and the cap is 250 runners. The race may take a few more than 250 to allow for no-shows, aiming at a starting field of 250, and in 2026 it sold out by early April, after which a waitlist opened. There are no refunds, no deferrals and no race-day entry.