Bear 100 — Utah and Idaho's Autumn Monster
Fall Colors and Brutal Ridgelines
Bear 100 runs through the Bear River Mountains straddling the Utah-Idaho border, starting in Logan, Utah and finishing in Preston, Idaho. Late September in these mountains means peak fall color — aspen groves turning gold, clear skies, cool temperatures at the start that turn cold at night on exposed ridges.
It also means unpredictable weather. Bear 100 has seen snow on the upper ridges. It has seen mud that makes the descents treacherous. September in the Bear Rivers is not a guaranteed mild experience.
The race has been running since 2007 and has built a loyal following among runners who want a serious mountain hundred without the lottery gauntlet of Western States or Hardrock.
The Course
The course runs point-to-point from Logan Canyon through the Bear River high country into Idaho. It covers 22,000 feet of gain — placing it firmly in the harder tier of American 100-milers, comparable to Wasatch Front in total climbing volume.
Logan Canyon (Miles 0-15): The race begins in Logan Canyon and immediately climbs. The opening miles establish the pattern: gain and loss, gain and loss, on rocky mountain trail.
High Ridgelines (Miles 20-60): The middle section traverses high ridges above 8,000 feet. These sections offer the race’s most dramatic views — and its most exposed terrain. Wind on the high ridges in late September can be sharp. Layers matter.
The Aspen Sections: Several portions of the course run through dense aspen groves that turn gold and orange in late September. Bear 100 is frequently cited as one of the most visually beautiful 100-milers in America. The beauty does not make it easier.
The Idaho Descent (Miles 75-100): The final section descends from the Utah-Idaho border into the Preston Valley. Long, sustained descents on tired legs. Quad management across the entire race determines how the last 25 miles feel.
Cutoffs and Character
Bear 100 has a 36-hour cutoff. Aid station cutoffs are enforced. The race is known for its well-organized crew access and community atmosphere — smaller than Leadville or Western States, more intimate, with a tight volunteer network that reflects the race’s deep regional roots.
What Makes Bear 100 Worth Running
It is not the most famous 100-miler. It does not offer Golden Tickets or national attention. What Bear 100 offers is a genuine mountain hundred — serious climbing, serious weather exposure, serious terrain — without the lottery wait of the marquee races. For runners who have completed more accessible 100-milers and want the next level, Bear is a direct answer.
The late September timing places it perfectly for runners building toward fall racing or closing out a strong summer training block. The fall color is real and it is remarkable.
100 miles | 22,000 ft gain | Late September | Logan, UT to Preston, ID | Running since 2007