In the world of trail ultrarunning, certain 100-mile races stand out for their enduring legacy, rich history, and contributions to the sport. Below is a log-style list of the most historically significant 100-mile trail ultramarathons in North America. Each entry highlights key facts – founding year, location, notable features, and the race’s impact on the ultrarunning community.

10. Haliburton Forest 100 Miler – Ontario, Canada (Est. 1993)

• Year Founded: 1993
  
• Location: Haliburton Forest, Ontario, Canada – a private 100,000-acre wilderness preserve in central Ontario’s highlands
  
• Notable Features: The Haliburton Forest Trail Race offers multiple distances, with the 100-mile ultra being its crown jewel . The course is a 25-mile figure-eight loop repeated four times, winding on logging roads and technical forest trails through dense woods, around sparkling lakes, and over rolling Canadian Shield terrain. Runners face rocks, roots, and short steep climbs (total elevation gain is modest relative to mountain races, but the constantly rolling terrain and technical footing make it challenging). The wildlife and scenery add to the experience – it’s not uncommon to hear wolves howling at night or to spot deer and foxes on the trails. The race is typically held in early September, so runners get a taste of cool Canadian fall nights after warm days. Haliburton’s finish rate is helped by its relatively generous 30-hour cutoff and a very runner-friendly setup (pacers allowed in latter stages, well-stocked aid every few miles).
  
• Contribution: Haliburton Forest 100 was a trailblazer for Canadian ultrarunning. As of its inaugural run in 1993, Canada had very few (if any) 100-mile trail races – Haliburton proudly calls itself the first such event in the country. Over the years, it has grown steadily, nurturing an ultrarunning community in Ontario and drawing participants from the U.S. as well . The event showcased that world-class ultras aren’t limited to mountains or deserts; lush forests can host epic endurance feats too. Haliburton also integrated multiple race distances (from 12K up to 100M) early on, introducing many trail runners to ultras stepwise and thus expanding the participant base. The race organizers’ focus on a friendly, family-like atmosphere – post-race barbeques, personalized encouragement, etc. – has set a standard for hospitality in ultras. Moreover, by being on private land, Haliburton demonstrated a model for partnerships between race directors and landowners, ensuring sustainability and minimal environmental impact (a model now seen in other private-lands races).
  

Historical Importance: Now over 30 years running, the Haliburton Forest 100 Miler stands as a piece of North American ultra history by virtue of being Canada’s oldest 100-mile trail race . It effectively put Canada on the 100-mile map and has since inspired other Canadian ultras (such as Sinister 7 100M in Alberta and Fat Dog 120 in BC). For Canadian runners, Haliburton became what Western States or Leadville was in the U.S. – a rite of passage and a source of national pride. The race’s legacy is also tied to its remote, beautiful setting: finishing 100 miles in Haliburton’s “lord of the rings” style wilderness imparts a special kind of confidence and lore. Event organizers can look to Haliburton as an example of building legacy through local culture: it leveraged what Ontario offered (thick forests, welcoming communities, adventurous spirit) to create an event that stands shoulder-to-shoulder with older U.S. races in terms of respect and tradition. In shaping the ultrarunning scene, Haliburton opened the door for ultras in every corner of North America – proving that passion, not just altitude or latitude, is what makes a 100-miler truly great.

9. Arkansas Traveller 100 – Arkansas (Est. 1991)

• Year Founded: 1991
  
• Location: Ouachita National Forest, Arkansas – a single-loop/traverse through the rolling Ouachita Mountains near Lake Sylvia
  
• Notable Features: Around 12,000 feet of elevation gain spread over gently rolling hills, making it less mountainous than Western ultras but by no means easy. The course follows a mix of forest service roads, jeep trails, and some single-track. October weather in Arkansas can be warm and humid in the day, cooling at night. Known for its down-home charm, the Arkansas Traveller 100 (AT100) offers runners Southern hospitality at aid stations and a fairly runnable course by 100-mile standards (leading to higher finisher rates than many mountain races). The cut-off is 30 hours. AT100 is often recommended as a great “first 100 miler” for those stepping up to the distance, thanks to its supportive atmosphere and moderate terrain .
  
• Contribution: By the early 1990s, ultras were spreading, and AT100 played a pivotal role in bringing 100-milers to the U.S. South. Its inaugural running in ’91 meant that, “by 1991… there existed at least eight big-name 100 milers around the country,” with Arkansas Traveller joining the ranks of Western States, Leadville, Old Dominion, Wasatch, Angeles Crest, Vermont, and Mohican . The Traveller thereby expanded the geographic reach of the sport. It also stepped up in 2008 when Western States was canceled due to wildfires – AT100 served as an alternate for Grand Slam aspirants that year , underscoring its reliability and importance in the ultra calendar. Community-wise, AT100 is organized by a passionate local ultrarunning club and has emphasized volunteerism and mentorship (many runners from across the country have been hosted or paced by generous locals). The race showcases how a regional event can adopt ideas from older races – belt buckle awards, pre-race pasta dinner, post-race breakfast – and create a longstanding tradition.
  

Historical Importance: Over 30+ years, the Arkansas Traveller 100 has become a beloved classic that’s put the Ouachitas on the ultrarunning map. Historically, it demonstrated the viability of 100-milers in areas without towering peaks – proving that dense forests and rugged backroads could challenge runners plenty. Many future race directors in the South and Midwest cut their teeth at AT100, learning how to organize ultras with a personal touch. The event’s spirit is encapsulated by its co-founder Lou Peyton (one of the first women to run multiple 100s), who helped ensure AT100 would welcome newcomers and veterans alike with open arms. In the broader scheme, while AT100 might not have the high-profile cachet of Western States or Hardrock, it has quietly shaped ultrarunning in the central U.S., building a bridge from the sport’s Western origins to the hardwood forests of the East. Its inclusion in challenges like the “Great Eight of UltraRunning” (the eight original 100s) attests to its legacy. For any organizer, the Traveller exemplifies how consistency, warmth, and regional pride can yield an event that stands the test of time.

8. Barkley Marathons – Tennessee (Est. 1986)

• Year Founded: 1986
  
• Location: Frozen Head State Park, Tennessee – unmarked loop course through dense Appalachian terrain
  
• Notable Features: An infamously difficult 100-ish mile event consisting of five 20+ mile loops with no official trail markings. The Barkley has ~60,000 feet of total elevation change packed into its distance – a brutal mix of steep climbs (often off-trail), thick brush, and unpredictable weather. The time limit is 60 hours, and aiding or pacing is not allowed. The race’s entry process is deliberately secretive and quirky (involving an essay, a license plate from your state, and acceptance by the director) . With a starting signal by the lighting of a cigarette, and tasks like tearing pages from hidden books on course as proof of reaching checkpoints, the Barkley is as much a mental puzzle as a physical trial. It is often nicknamed “The race that eats its young,” reflecting its extremely low finisher rate – in over three decades, only 20 individuals have ever finished within the cut-off (and some years, like 2022 and 2023, see zero finishers) .
  
• Contribution: Though on the fringe, the Barkley Marathons has contributed disproportionately to ultrarunning folklore and mystique. Created by Gary “Lazarus Lake” Cantrell, it was inspired as a tongue-in-cheek challenge after a famous prison escapee barely covered 8 miles in the same woods – Laz quipped he could do 100, and thus the Barkley was born . The race introduced a spirit of dark humor and creativity into ultrarunning: it showed that an event could outright reject commercialization and still gain global fame. The Barkley’s success (or infamy) has inspired a subgenre of “extreme ultras” that emphasize navigation, self-reliance, and absurd difficulty – for example, races like Big’s Backyard Ultra (another Laz creation) and Europe’s Tor des Géants owe a nod to the Barkley’s concept. Media coverage, including a popular documentary, turned the once-obscure race into a wider inspiration: many non-ultrarunners know of the Barkley, and its lore (“books”, “campsite”, “fun run” for 60 miles) has trickled into mainstream endurance conversations.
  

Historical Importance: The Barkley Marathons holds a unique place as a living legend of ultrarunning eccentricity. First held in 1986, it predates many 100-milers, but for years was an underground phenomenon with no finishers until 1995 . Its perseverance and growing cult status through the ’90s and 2000s demonstrated that the ultrarunning community has room for wildly unconventional challenges alongside standard races. In historical context, Barkley didn’t shape the mainstream ultrarunning scene so much as it shaped the narrative and identity of the sport’s extreme fringe. It reminds everyone that ultrarunning’s roots lie in exploration of limits, absurd as that may sometimes be. For race directors, Barkley is a case study in how anti-establishment ethos and creative course design can yield an event so iconic that it doesn’t need sponsors or prizes – its legend is the reward. In sum, the Barkley Marathons has transcended its status as an ultra—becoming a metaphor for the ultimate test of endurance and adventure, and thereby etching its story into North American ultra history.

7. Hardrock Hundred Endurance Run – Colorado (Est. 1992)

Runners carefully descend a steep scree field at 12,900 ft on the Hardrock 100 course (Grant Swamp Pass). Founded in 1992 as an homage to Colorado’s mining past, Hardrock’s extreme altitude and rugged terrain have earned it a mythical status in the ultrarunning community.

• Year Founded: 1992
  
• Location: San Juan Mountains, Colorado – a 102.5-mile loop starting and ending in Silverton, CO, passing through Telluride, Ouray, and historic mining ghost towns
  
• Notable Features: The most extreme elevation profile of any classic 100: ~33,000 feet of climb and descent, with an average elevation over 11,000 ft . The high point is 14,048 ft at Handies Peak, and runners frequently deal with thin air, mountain storms, snowfields, and wild stream crossings . Cut-off time is a lengthy 48 hours, acknowledging the race’s difficulty – and indeed, many finish just under that, seeing the sun rise twice. Instead of a finish line banner, athletes must “kiss the Hardrock,” a painted boulder, to officially finish . Entry is via a notorious lottery with qualifying requirements (you must complete other tough mountain 100s first), which has created an aura of exclusivity and honor around the race.
  
• Contribution: Hardrock was conceived to celebrate the hard-rock mining heritage of Southwestern Colorado and the grit of the miners who built its trails . Founders Gordon Hardman, John Cappis, and others wanted a super-tough mountain ultra as a “post-graduate” challenge beyond Western States or Leadville . In doing so, they pushed the boundaries of what an organized ultra could be. Hardrock’s institution of service requirements (expecting entrants to volunteer in the trail community) and its focus on veteran mountain ultra experience set new standards for race ethos. Culturally, Hardrock inspired a generation of arduous mountain ultras around the world (many now speak of events as “Hardrock-style”). It also forged the “Rocky Mountain Slam” challenge (Hardrock plus three other Rocky Mountain 100s) , encouraging more growth of difficult courses. Hardrock’s community is famously tight-knit: volunteers and runners return year after year, fostering traditions like the pre-race “Camp Hardrock” trail work and the post-race awards where each finisher is treated like a hero.
  

Historical Importance: In just over 30 years, Hardrock 100 has attained a nearly mythical reputation – often called one of the world’s toughest ultramarathons. Its introduction in 1992 marked a shift toward embracing extreme adventure in ultrarunning. The event pays homage to the past (honoring 19th-century miners) while simultaneously representing the sport’s future (extreme athletics in wilderness). Hardrock’s prestige is evidenced by the demand for entry – lotteries with minuscule acceptance rates – and by elite athletes coveting a finish here more than a podium elsewhere. Despite cancellations in a few years (snow in 1995 and 2019, fire in 2002, pandemic in 2020) , Hardrock has remained the definitive high-mountain ultra. For event organizers, it exemplifies how a clear identity and mission – in this case, “Wild & Tough” mountain adventure – can elevate a race to legendary status. Its “esprit de corps,” forged at altitude, has profoundly shaped ultrarunning culture, emphasizing humility, resilience, and reverence for the mountains.

6. Angeles Crest 100 Mile Endurance Run – California (Est. 1986)

• Year Founded: 1986
  
• Location: San Gabriel Mountains, Southern California – from Wrightwood to Altadena (near Los Angeles)
  
• Notable Features: A point-to-point mountain course with about 19,000 feet of ascent and a 33-hour cutoff. AC100 was designed as a challenging “Western States qualifier” for SoCal, originally with a 30-hour target (later extended due to difficulty) . Runners climb several major peaks (like Mt. Baden-Powell at 9,300 ft) and endure high summer temperatures, especially in lower canyons. The course has seen modifications over time due to wildfires (e.g., detours for endangered frog habitat and fire damage) . AC100 is limited to ~150 runners and requires a prior 50-mile finish to enter , reflecting its tough nature. Finishers earn hand-crafted buckles and a unique “Ram’s Head” trophy for certain time brackets, adding to the race’s character.
  
• Contribution: Angeles Crest brought the 100-mile phenomenon to Southern California’s front yard. Conceived by Ken Hamada (who remains the race director into his 80s) , AC was the sixth 100-miler to emerge in the US, completing the early canon of “original 100s.” It quickly became known for community spirit – the co-RD Hal Winton (for nearly 30 years) and Hamada fostered a family-like volunteer culture. AC100 also spawned the idea of the “Last Great Race,” a challenge to run the first six 100-milers (OD, WS, VT, AC, Leadville, Wasatch) in one summer . Over the years, AC faced adversity (notably wildfires forcing cancellations in 2002 and 2009, and again climate-related cancellations in recent years) . Each time, organizers adjusted the course or schedule to persevere, illustrating resilience.
  

Historical Importance: Angeles Crest 100 holds a revered spot as one of America’s original mountain 100s, bringing legit ultrarunning to Los Angeles’s backyard. Its history is interwoven with the sport’s expansion in the late ’80s. For Southern California runners who couldn’t travel to the Sierra or Rockies, AC offered a classic 100-mile test on home turf – effectively democratizing the 100-mile distance. The race’s nearly four decades of continuity (barring a few fire/pandemic interruptions) demonstrate how a regional ultra can attain national prestige by staying true to its mission. AC100 is often remembered for its personalized touches: Hamada’s hands-on directing, custom awards, and the motto that “you’ve got to have risks” to achieve greatness . In an era of increasing commercialization, Angeles Crest remains a beacon of the old ways, proving that authenticity and challenge breed lasting fame. It has shaped the ultrarunning scene by mentoring generations of runners and race directors in how to blend big ambition with a close-knit community vibe.

5. Wasatch Front 100 Mile Endurance Run – Utah (Est. 1980)

Finish of the Wasatch Front 100 – a banner proclaiming “100 Miles of Heaven and Hell” greets runners. Established in 1980 in Utah’s Wasatch Mountains, this race remains unapologetically tough and true to its roots.

• Year Founded: 1980 (first running – 5 starters, 2 finishers) ; officially recognized by 1983
  
• Location: Wasatch Mountains, Utah – a point-to-point traverse from the eastern slopes near Kaysville to the finish in Midway, UT
  
• Notable Features: Slogan: “One Hundred Miles of Heaven and Hell.” Wasatch earned a reputation as one of the toughest 100-milers in the U.S. . The course packs in ~24,000 feet of climb and similarly brutal descents, topping out above 9,000 ft elevation. Runners face remote, wild terrain – from alpine ridges to deep canyons. The cut-off is 36 hours, but the average finish hovers around 33-34 hours, reflecting the difficulty. Aid is sparse compared to modern races, and weather can range from hot valleys to cold mountain nights. The race deliberately keeps a low profile (no live tracking or big expos), emphasizing personal challenge over fanfare.
  
• Contribution: Wasatch Front was the third 100-miler established in the USA , modeled after Western States and Old Dominion but upping the ante with more rugged mountains. It helped pioneer the concept of truly remote, wilderness ultras – in 1980, five intrepid runners attempted what many deemed “impossible,” finishing through sheer resolve . The race also became the traditional culmination of the Grand Slam of Ultrarunning each year (being held in early September). Its strict yet understated organization, embodied by longtime RD John Grobben, has influenced how later ultras balance safety with self-sufficiency. Wasatch’s famous tagline, “100 miles of heaven and hell,” set the tone for how ultras could honestly advertise their severity while building camaraderie among those who dare to enter .
  

Historical Importance: Celebrating over 40 years, Wasatch Front 100 stands as a testament to consistency in the sport. It has changed remarkably little since its inception – a fact celebrated during the race’s 40th anniversary when veteran “pioneers” were invited back to run on a special 40-hour early start . This race has never lost its soul: no prize money, minimal media, and a pre-race briefing where “fast and famous” runners remain unintroduced . Such old-school purity has preserved the spirit of ultrarunning’s early days. Wasatch taught the community that an ultra can be an intimate, back-to-basics experience even as the sport grows. Its legacy lives on every time runners battle through its heaven-and-hell course, forging lifelong bonds on the trail. As an organizer, looking at Wasatch is to see how tradition and challenge, when kept at the core, create enduring prestige

4. Old Dominion 100 Mile Endurance Run – Virginia (Est. 1979)

• Year Founded: 1979
  
• Location: Woodstock, Virginia – in the Shenandoah Valley and Massanutten Mountains of Virginia
  
• Notable Features: Old Dominion traces a 100-mile loop of country roads, horse trails, and mountain paths with about 14,000 feet of elevation gain. It traditionally starts and ends at the county fairgrounds in Woodstock. Known for its hot, humid weather and a strict 28-hour cutoff, OD challenges runners with both climbs and long stretches of runnable terrain. The event’s aesthetics are modest and low-key – no extravagant expos or crowds, just rural Virginia landscapes and minimally catered aid stations reflecting its old-school ethos .
  
• Contribution: As the second-ever 100-mile trail race in the USA (after Western States) , Old Dominion proved that the 100-mile format could thrive beyond the West Coast. It was one of the original four mountain 100s and gave East Coast ultrarunners their own classic event starting in the late 1970s . OD’s philosophy emphasizes grit and self-reliance – for many years, it allowed limited crew access and minimal aid, reinforcing a culture of tough, self-supported runners. The race became part of the first Grand Slam of Ultrarunning (and later an option in that series) and helped spur the creation of other Eastern ultras.
  

Historical Importance: Old Dominion’s enduring legacy lies in its contrast with Western States. While Western States grew into a large, spotlight event, Old Dominion steadfastly preserved the original spirit of ultrarunning – “a test of grit and self-reliance” as it was designed . Over four decades, OD has weathered changes without losing its grassroots character: no corporate frills, low entry fees, and even finishing awards like engraved pewter horse plaques that hark back to its equestrian roots. It stands as a living museum of ultrarunning’s heritage. For event organizers, Old Dominion offers a case study in longevity through simplicity. By 1979, it boldly extended the 100-mile challenge to new terrain, and in doing so, cemented itself as a pillar of ultrarunning history – “one of the original four 100-mile trail races” in America and the genesis of 100-milers on the East Coast.

3. Vermont 100 Mile Endurance Run – Vermont (Est. 1989)

• Year Founded: 1989 (foot race; building on a 100-mile equestrian ride from the late 1970s)
  
• Location: Windsor, Vermont – rolling hills, farms, and forests of New England (start/finish in Silver Hill Meadow)
  
• Notable Features: ~15,000–17,000 feet of elevation gain on a mix of country dirt roads and trails . Famous for its horse-and-runner format – the Vermont 100 is one of the world’s only ultras where runners race simultaneously alongside horses over portions of the course . It’s also known for its pastoral scenery and humid summer weather, with deceptively hard terrain (mud, hills) hidden among the green Vermont countryside.
  
• Contribution: Vermont 100 has a proud legacy of inclusivity and community. It was the first ultra to formally include visually and mobility-impaired runners with dedicated awards categories . From its inception, it partnered with Vermont Adaptive Ski & Sports, making the race a major fundraiser for athletes with disabilities . Culturally, Vermont brought 100-milers to New England and became the only East Coast race in the Grand Slam of Ultrarunning (after 1989) . Its unique pairing of horses and runners harkens back to the sport’s roots and Western States’ origins, thus preserving the historical connection between endurance riding and ultrarunning.
  

Historical Importance: Despite starting later than some Western races, the Vermont 100 quickly secured its place as one of the classic 100-milers in America. It is one of the oldest 100-mile runs in the country and for years was the sole 100-miler in the eastern U.S. Grand Slam . Founded by Laura Farrell (who was herself a veteran of Western States and the Tevis Cup), the event carried forward the frontier spirit of the original ultras, but on New England soil . Over three decades, Vermont has shaped ultrarunning by demonstrating that a race can be simultaneously tough, inclusive, and tied to a charitable mission. Its continuous operation (every year since 1989, barring 2020’s pandemic cancellation) and its emphasis on “old-school” hospitality have solidified its prestige. Today, the Vermont 100 is revered for its history and 100-mile “grassroots” feel, offering a living link to the early days of American ultrarunning .

2. Leadville Trail 100 “Race Across The Sky” – Colorado (Est. 1983)

• Year Founded: 1983
  
• Location: Leadville, Colorado – out-and-back through the heart of the Rocky Mountains, starting at 10,200 ft elevation
  
• Notable Features: High-altitude course with ~15,700 feet of cumulative gain, including the iconic 12,600-ft Hope Pass climbed twice . Runners face thin air and rugged trails; fewer than half typically finish under the 30-hour limit . The race’s reputation was boosted by the epic wins of Tarahumara runners in the 1990s, as popularized in mainstream books.
  
• Contribution: Leadville was conceived by local leaders to revive a mining town’s economy after a mine closure – a pioneering example of an ultra as community salvation . Co-founder Ken Chlouber famously said, “You’re tougher than you think you are, and you can do more than you think you can,” encapsulating the spirit that Leadville instilled in the sport. The race helped expand ultrarunning beyond the coasts and showed that well-organized 100-milers could draw participants to remote areas. It also spawned the Leadville Trail Series (including a 100-mile MTB race) and the idea of the “Leadman” multi-race challenge.
  

Historical Importance: As one of the four original 100s in the “Grand Slam of Ultrarunning” , Leadville quickly gained prestige in the 1980s. It was among the first high-altitude ultras open to all, proving that large fields could tackle extreme elevations. By hosting the first indigenous Tarahumara runners’ appearances in U.S. ultras (1992–94), Leadville bridged cultures and inspired a boom in interest in trail ultras . Celebrating its 40th anniversary in 2023, Leadville remains an iconic “race across the sky” – a testament to endurance and a cornerstone of ultrarunning history.

1. Western States Endurance Run – California (Est. 1977)

• Year Founded: 1977 (first completed on foot in 1974 by Gordy Ainsleigh)
  
• Location: Sierra Nevada, California – point-to-point from Olympic Valley to Auburn
  
• Notable Features: ~18,000 feet of climb, intense summer heat in the canyons, and iconic river crossings. Famous for its 24-hour silver belt buckle tradition for finishers .
  
• Contribution: Widely regarded as the world’s oldest 100-mile trail race , Western States set the standard for modern trail ultras. It was born from the 1950s horseback Tevis Cup route and evolved into an official footrace by the late 1970s, inspiring hundreds of other ultras worldwide . Its growth (now a globally followed, lottery-entry event) helped transform ultrarunning from a niche endeavor into a popular endurance sport .
  

Historical Importance: Western States is the foundational 100-miler, often called the “granddaddy” of trail ultras. It marked the dawn of mountain ultrarunning in 1977, proving that 100 miles on foot in one day was humanly possible . Over nearly five decades, it has remained one of the most prestigious ultras , home to legendary competitions and an ever-growing volunteer and runner community. Its origin story – Gordy Ainsleigh’s solo run during a horse race in 1974 – has become lore, symbolizing the birth of the sport in the USA. Western States’ legacy lives on each June as 369 runners take on “100 miles One Day” across the Sierra Nevada, cementing its status as a pinnacle of ultrarunning .

Sources: The information above is drawn from historical accounts, official race data, and reputable ultrarunning publications, including Western States Endurance Run archives , UltraRunning Magazine and iRunFar features on classic races , and other authoritative sources that document the rich history of these events . Each race’s founding and significance have been cross-referenced with primary sources to ensure accuracy. Together, these ten races represent the backbone of 100-mile trail running in North America, each contributing a chapter to the sport’s ongoing story.