Mount Desert Island Marathon

The Mount Desert Island Marathon (MDI) is Maine's premier destination marathon, run each October on the weekend following Indigenous Peoples' Day along the rugged coastline of Mount Desert Island near Acadia National Park. The USATF-certified 26.2-mile course starts in downtown Bar Harbor, climbs over Champlain and Dorr Mountains in the opening miles, passes Somes Sound (the only fjord on the U.S. Atlantic coast), and finishes in the maritime village of Southwest Harbor, with the toughest hills concentrated in the final 10K. A companion Half-Marathon starts in Northeast Harbor, and a 3-Person Relay lets teams split the marathon course; all events share the Southwest Harbor finish and peak fall-foliage scenery. The race is a direct Boston Marathon qualifier, though its hilly terrain makes it a tougher BQ attempt than flat courses. Registration is capped and has closed early in past years, so organizers recommend signing up well ahead of the October 18, 2026 race day.