100K January ultramarathons in United States

Lakefront trails through Arkansas Bend Park, skirting the Colorado River and limestone bluffs, with natural terrain and unique endurance formats.

Dynamic loops at Shaffer Bend Park along limestone bluffs and the Colorado River, sun-bleached trails, lush scenery, and manageable elevation per loop

Looped trail course over sun-bleached limestone bluffs, riverside paths, and Colorado River views, with moderate elevation changes and stargazing opportunities

Flat, open route on the Northeast Texas Trail with gravel, dirt, pavement, and grass sections through small towns and rugged backcountry

Rugged Texas Hill Country trails, rocky paths, thorny foliage, and technical terrain amid striking natural scenery

Rugged technical trails through rocky paths and steep climbs in Texas Hill Country, featuring the challenging Bandera 100k and non-competitive 50k courses

Multi-day ultramarathon series including a 200-mile, 100-mile, and 100 km race, with staggered starts and challenging distance courses.

6.5-mile loop in Vermont's Green Mountains with 1200 feet of elevation gain, expansive views, and variable winter conditions

Desert singletrack and foothill paths in Estrella Mountain Regional Park, with Sonoran scenery and 100K or 100-mile options.

Rugged multi-loop course through rolling wooded hills, creek bottoms, and pine floors with up to 15,000 feet of elevation change near St. Louis

Two-loop ultramarathon from Emma Carlin, including Ice Age Trail to Whitewater and Scuppernong Trails, remote terrain, self-supported with aid stations

Loopy dirt and rocky singletrack in Bastrop State Park, with pine forest scenery, steady hills, and rolling Central Texas terrain.

Remote desert trails across Big Bend’s rugged terrain, scarce resources, panoramic vistas, and exceptional night skies under minimal light pollution

Rocky desert singletrack, big elevation, demanding climbs, and a summit section with expansive views across four states

Rugged Santa Monica Mountains singletrack on the Backbone Trail, with ocean views and nearly 11,000 feet of climbing on the 50-mile course.