The One Day Hike (ODH) comprises two concurrent, non-competitive hikes of 100 and 50 km (62.14 and 31.07 miles) that follow the C&O Canal towpath, and end in Bolivar, WV. The 100 km event (“100K”) starts at 3 AM from the Thompson Boat Center parking lot in Georgetown, Washington, DC; the 50 km event (“50K”) starts at 10 AM from Whites Ferry in Montgomery County, MD. Both hikes proceed along the towpath, crossing the footbridge into Harpers Ferry after mile marker 60, ending at the Bolivar Community Center. Hikers have until midnight to complete either hike.

All hikers must be pre-registered, and are required to sign in at the start. During the hike, they pass through support stations manned by volunteers, where they are logged in and out, provided with food and drink and, if necessary, first aid assistance. While on the trail, they are monitored by volunteer bike patrols and volunteers can assist hikers that drop out before the end. Hikers that do finish get a 100K or 50K patch to recognize their accomplishment.

The ODH may well be the mid-Atlantic region's oldest long-distance hike, the 100K having been held since 1974, and the 50K since 2000. All but 1.5 miles of each hike takes place within the C&O Canal National Historical Park. Hikers then walk through part of the Harpers Ferry National Historical Park, before finishing at Bolivar.

The 2013 One Day Hike is scheduled for Saturday, April 27, 2013.