A marathon ends in a few hours. These races end in days, and in two cases, weeks, with no aid station, no support crew, and no clock that stops when the sun goes down.
Tour Divide
Mountain bikers race 2,745 miles from Banff, Alberta to Antelope Wells, New Mexico, following the Great Divide Mountain Bike Route down the spine of the Rockies. The clock starts at the border crossing and doesn't stop, riders sleep in gas station doorways and forest-service pullouts, resupply in whatever small town happens to be next, and climb more than 200,000 feet before they're done. Mike Hall set the current record in 2016: 13 days, 22 hours, 51 minutes. Most finishers take three to four weeks.
Trans Am Bike Race
The Trans Am covers roughly 4,200 miles on pavement, from Astoria, Oregon to Yorktown, Virginia, along the Adventure Cycling Association's 1976 TransAmerica Bicycle Trail through ten states. Like the Tour Divide, it's self-supported and continuous, no team cars, no drafting, no scheduled rest. The distance alone puts it ahead of the Divide; the tradeoff is asphalt instead of gravel and singletrack.
Yukon 1000
Boat hulls replace bike tires for 946 miles of the Yukon River, from Whitehorse, Yukon to Circle, Alaska, through subarctic and then arctic wilderness, unsupported the entire way. It's billed as the longest canoe and kayak race in the world, and the isolation is the real obstacle: long stretches with no road access, no cell coverage, and no way to quit except finishing or getting pulled by a safety boat.
Missouri River 340
The MR340 covers 340 miles down the Missouri River, from Kansas City, Kansas to St. Charles, Missouri, with a roughly 85-hour cutoff and day and night paddling on a working river that doesn't pause for racers. It's shorter than the Yukon 1000 but faster-paced by design, a cutoff clock instead of an open one, and it's the longest continuous canoe and kayak race in North America outside Alaska and the Yukon.
Cocodona 250
Running shoes take over for the last two entries, starting in Arizona. Cocodona 250 covers 250 miles point-to-point from Black Canyon City to Flagstaff, climbing out of Sonoran desert into high-elevation pine forest along the way. The terrain change is the story: cactus and slickrock at the bottom, snow at the top possible even in late spring, in the same race.
Moab 240
The Moab 240 covers 240 miles through Utah's red-rock canyon country, the shortest race on this list by mileage and one of the newest by age, part of a wave of 200-plus-mile trail races that didn't really exist in the U.S. before the mid-2010s. Runners are typically out for two to four days straight, napping in aid stations or on the trail itself rather than stopping to sleep in any real sense.
None of these races have a finish-line party that starts on schedule. Mike Hall crossed the Tour Divide's line in under 14 days; most Moab 240 finishers are still moving after two. The clock is the only constant.
Hero photo: a loaded bikepacking rig in the mountains, by Lorenzo Rui on Unsplash.