Every third Sunday in October, tens of thousands of runners pour out of downtown Detroit before dawn and head for the river. They climb the Ambassador Bridge into Canada, drop down into Windsor, and then, somewhere around the middle of the race, they disappear beneath the Detroit River itself. When they emerge on the American side, they have run what the race likes to call the only official underwater international mile in the world.
That oddity is the signature of the Detroit Free Press Marathon, which returns for its 49th running on the weekend of Oct. 16-18, 2026. It is a race built on a geographic accident: Detroit and Windsor sit directly across from one another, separated by a river, connected by a bridge and a tunnel. Almost no other major marathon can route its field through two countries in a single morning. Detroit's does, and has for nearly half a century.
The marathon was established in 1978 and has used the Detroit-Windsor Tunnel in all but two years of its existence, according to the race's history. The current course crosses both the Ambassador Bridge and the tunnel. It is a USATF-certified, Boston-qualifying course, which matters to the sizable share of the field chasing a qualifying time for Hopkinton.
The weekend is far more than 26.2 miles. Saturday, Oct. 17, belongs to the shorter distances: a 1-mile race, a 5K, the Kids Marathon, and the Little Detroit Dash. Sunday, Oct. 18, is the main event, with the Marathon and International Half Marathon and the Motor City Half Marathon, which stays on the U.S. side of the border.
The binational route creates a rare logistical spectacle. The Detroit-Windsor Tunnel closes to motorists while runners pass through. Part of the Ambassador Bridge closes too, with traffic alternating on one side of the span. In Detroit, downtown corridors shut down for the route.
For spectators, the race is free to watch, and the after-party is free to attend. Kia Conquered runs Sunday at Campus Martius, with food trucks, a live performance, on-stage awards, beer and other drinks, and photo opportunities. Live runner tracking is available through the official race app, and results post to the marathon's website.
The event's recent rise has been steep. In April, the Detroit Free Press Marathon was named the best marathon in the United States by the USA TODAY 10Best Readers' Choice Awards, beating a field of 20 races that included the Chicago, Boston, and New York City marathons. It was the second consecutive year Detroit took the honor, making it the first race to win the award back-to-back.
Vice President and Race Director Aaron Velthoven called the repeat recognition a reflection of the region. "To be the first race to win this award back-to-back is truly special," he said. "It speaks to what an amazing race we have here in Detroit and in Windsor, this great binational region that celebrates running."
The award has had a measurable effect on demand. The 2025 race drew more than 26,000 runners from around the world, including about 4,000 Canadians, and sold out by March. Registration for 2026 opened on Jan. 1 and filled in roughly a week, even after organizers added capacity. Velthoven said the 2026 edition will be the largest in the race's 49-year history, with close to 30,000 participants. The Sunday races, including the marathon and both half marathons, are sold out.
That growth has created a need off the course as well. Organizers are recruiting more than 3,000 volunteers for race weekend, with the greatest demand on Sunday, Oct. 18, when the marathon and half marathons fill the streets. The volunteer push, announced in August, reflects the scale the race has reached: a regional event that now requires a small army to move 30,000 people across an international border and back before lunch.
What has stayed constant is the course itself. The marathon's appeal rests on a stretch of road that no other American race can replicate, a few minutes of darkness under the river between two countries. Runners enter the tunnel in Canada and exit in the United States, and for that mile there is nothing to see but concrete, lights, and the sound of thousands of feet. It is, by the race's own accounting, the only official underwater international mile anywhere in the world, and it is the reason a mid-sized Midwestern marathon keeps landing at the top of national lists.