The Reluctant Discovery:

How Three Unheralded Montanans First Mapped the Wonders of Yellowstone

Introduction

In September 1869, three men rode south out of a fading Montana gold camp with borrowed provisions, no official backing, and a plan considered reckless by nearly everyone who heard it. They were not soldiers, scientists, or men of public standing. They were a surveyor, a merchant, and a laborer, and they intended to see for themselves whether the fantastic stories drifting out of the upper Yellowstone country — boiling fountains, canyons of impossible depth, mountains that seemed made of glass — were fact or the invention of men who had spent too long alone in the mountains. Their journey, the Cook-Folsom-Peterson Expedition, would become the first sustained, deliberate exploration of the region that became Yellowstone National Park. It would also become one of the odder case studies in how difficult it can be for the truth to find an audience.

A Gold Camp on Borrowed Time

The expedition’s origins lie in Diamond City, a placer mining settlement in Confederate Gulch east of Helena. Named for the Confederate parolees who had prospected there after the Civil War, the gulch produced an extraordinary yield of gold in the years immediately preceding the expedition, and for a brief period rivaled any camp in Montana Territory in output (“Confederate Gulch”). A Montana Historical Society Library and Archives record notes that the initial 1864 strike drew roughly a thousand people into the gulch, while a separate regional history citing an academic account of the territory places Diamond City’s peak population closer to ten thousand — a discrepancy that appears to reflect different points in the boomtown’s rapid rise rather than a factual contradiction, though only the latter source offers the higher figure (“Confederate Gulch”; “Diamond City and Confederate Gulch”). By 1869, the easy gold was largely gone, and the camp’s fortunes were already declining, a decline that would be nearly total within a decade (“Diamond City and Confederate Gulch”).

It was against this backdrop of diminishing prospects that Charles W. Cook, a mining engineer, and David E. Folsom, a surveyor, found themselves with unclaimed time on their hands. Both men had originally hoped to join a larger, better-financed expedition to the Yellowstone country, one intended to be strong enough to deter any trouble with Native bands who traveled the region. That larger effort never materialized. Rather than abandon the idea, Cook and Folsom decided that a small, quiet party was less likely to draw notice than a large one, and William Peterson, a Diamond City acquaintance who worked for Cook, agreed to round out the group (Miller).

Departure and the Skepticism of Friends

The three men left Diamond City on September 6, 1869, riding south with pack animals and roughly six weeks of provisions. Cook later recalled the send-off in terms that undercut any notion of a triumphant departure. Friends who gathered to see them off offered warnings rather than encouragement, telling the men to look out for their scalps and predicting that if they returned at all, they would come back on foot, having lost their horses along the way (“The Folsom Party”). The expedition, in Cook’s own later description, had none of the prestige originally attached to a grander, planned venture; it was, in his words, of no importance to anyone but the three men undertaking it.

Their route took them south through Crow Creek, then down toward the Gallatin Valley, where they stopped in Bozeman to secure additional supplies. There they tried and failed to recruit local men to join them, but did gain something more valuable than manpower: information from George Phelps, a prospector who had traveled through the Yellowstone region years earlier during the breakup of an 1864 expedition led by James Stuart (“The Folsom Party”). From Bozeman, the party followed a miner’s trail toward the Yellowstone River, entering the region that would become the park by crossing Mount Everts and the Blacktail Deer Plateau.

Into the Wonderland

What followed was five weeks of travel through terrain none of the three had any reliable map to guide them through. Their account, later assembled from the diaries each man kept independently, describes an early encounter with a band of Sheepeater Shoshone that proved friendly despite the men’s initial apprehension, and a landscape that alternated between grassy tablelands and canyon country so deep that, in their words, no one had ever found a way through it (Cook and Folsom). At the Grand Canyon of the Yellowstone, the party paused for an extended examination of the cliffs, noting with a surveyor’s precision the layered basalt and conglomerate in the canyon walls and a peculiar freestanding pinnacle of stone rising from the riverbed (Cook and Folsom).

The party pressed on through hot spring basins they nicknamed the Chemical Works, through sulfur beds and mud volcanoes, and past the falls of the Yellowstone, which Cook and Folsom’s account describes in restrained but evidently moved terms as a scene surpassing any description they felt equal to providing. They reached Yellowstone Lake on September 24 and rested along its shore for several days, recording thermal features along the lakebed and marveling at the abundance of trout and waterfowl. Turning homeward at the end of September, the men crossed toward the Madison River drainage and passed through a geyser basin they recognized, from earlier secondhand reports, as the place known as Burnt Hole or Death Valley — very likely an early encounter with what is now the Lower Geyser Basin. There they watched an intermittent geyser erupt to a height they estimated at eighty feet (Cook and Folsom). The party arrived back in Diamond City on the evening of October 11, thirty-six days after setting out, just as friends at home were organizing a search party on the assumption that the three men were lost or dead (“The Folsom Party”).

A Story No One Wanted to Print

The men’s reluctance to publicize what they had seen proved well founded. Folsom later admitted he doubted any magazine editor would treat a truthful account as anything but the exaggeration of what he called a typical Rocky Mountain liar (Miller). When a Montana acquaintance with publishing connections encouraged Cook and Folsom to write up their notes, the two combined their separate diaries into a single narrative and submitted it for publication. The New York Tribune, Scribner’s, and Harper’s all declined it, each citing a reputation they were unwilling to risk on material they considered unreliable (Miller). The account eventually found a home in the comparatively obscure Western Monthly Magazine of Chicago, which published it in July 1870 and paid the authors eighteen dollars for the rights (Miller; “The Folsom Party”). Even then, the magazine’s editor cut substantial portions of the manuscript, and credited the article to Cook alone, omitting Folsom and Peterson entirely.

The article’s difficult history did not end there. The Western Monthly’s offices burned in the Great Chicago Fire of October 1871. A copy Folsom had donated to the Montana Historical Society was destroyed in the Helena fire of 1874, and a copy he later lent to a professor at what is now Montana State University was lost in a 1916 fire that gutted the college’s chemistry building (Miller). When Nathaniel P. Langford republished the account in 1904 for the Montana Historical Society’s Contributions series, he overstated its rarity and again misattributed authorship to Folsom alone, an error made stranger by the fact that all three original expedition members were still living at the time (Miller). Decades later, historian Aubrey L. Haines undertook an exhaustive reconstruction of the expedition from surviving fragments and testimony, publishing The Valley of the Upper Yellowstone through the University of Oklahoma Press in 1965 — still regarded as the definitive scholarly treatment of the journey (Scott; “The Folsom Party”). A previously unknown manuscript version of the account, uncovered decades later, was subsequently acquired by Montana State University’s library, adding new material to a documentary record that historian Kim Allen Scott has described as unusually tangled even by the standards of frontier-era exploration narratives (Scott).

A Quiet but Lasting Influence

Despite its rough publishing fortunes, the expedition’s practical influence on Yellowstone’s future was considerable. On returning to Helena, Folsom took a position in the office of Montana’s Surveyor General, where he collaborated with fellow explorer Walter W. deLacy on a new territorial map that, for the first time, plotted the party’s route through the upper Yellowstone with reasonable accuracy, including the falls, the thermal basins, and the lake itself (“The Folsom Party”). That map circulated through the General Land Office and later accompanied the 1870 Washburn-Langford-Doane Expedition, whose members used it to identify a shortcut near Tower Fall that Henry Washburn climbed to confirm from the summit now known as Mount Washburn (“The Folsom Party”).

Just as important was the encouragement Folsom’s firsthand account gave to men of greater public standing. Folsom recounted his journey privately to a small circle of Helena acquaintances, including banker Samuel T. Hauser and Nathaniel Langford, who later credited that account with renewing his own determination to see the region — a resolve that led directly to the organization of the 1870 Washburn party, whose better-connected members succeeded in bringing Yellowstone to national attention where Cook and Folsom had failed (“The Folsom Party”; Miller). Some historians have also credited Folsom with an early, informal suggestion that portions of the Yellowstone region be set aside for public use rather than sold into private hands, an idea he reportedly raised with Washburn before the 1870 expedition departed — though this claim rests on Langford’s later recollection and appears in only one of the sources consulted here, making it worth noting as less firmly corroborated than the expedition’s other documented contributions (“The Folsom Party”).

Conclusion

The Cook-Folsom-Peterson Expedition never received the credit its members might have hoped for. Its principal written record was rejected by the era’s most influential publications, printed in a magazine soon lost to fire, and misattributed for decades afterward. Yet the expedition’s quieter legacies — an improved map, a body of firsthand testimony that reached the right ears in Helena, and the direct inspiration it gave to the far more celebrated Washburn party of 1870 — did more to shape the future of the Yellowstone region than its authors could have anticipated as they rode south from a played-out gold camp in the fall of 1869.

Works Cited

Confederate Gulch. Montana Memory Project, Montana Historical Society Library and Archives, www.mtmemory.org/nodes/view/127630. Accessed 2 Aug. 2026.

Cook, Charles W., and David E. Folsom. The Folsom-Cook-Peterson Expedition of 1869. Internet Archive, archive.org/stream/folsomcookpeters162slsn/folsomcookpeters162slsn_djvu.txt. Accessed 2 Aug. 2026.

Diamond City and Confederate Gulch, Montana Territory. Preserve Broadwater History, preservebroadwaterhistory.org/DiamondCity. Accessed 2 Aug. 2026.

The Folsom Party (1869). Yellowstone History, yellowstone.net/history/the-folsom-party-1869/. Accessed 2 Aug. 2026.

Miller, M. Mark. “Rediscovered Manuscript Describes 1869 Yellowstone Expedition.” Yellowstone Gate, 8 Nov. 2013, www.yellowstonegate.com/?p=9059. Accessed 2 Aug. 2026.

Scott, Kim Allen. “A Missing Piece of a Yellowstone Puzzle: The Tangled Provenance of the Cook-Folsom-Peterson Yellowstone Expedition Diary.” Yellowstone Science, Montana State University ScholarWorks, scholarworks.montana.edu/items/955d65c4-547e-44dc-be85-35643aebde41. Accessed 2 Aug. 2026.