Captain Clark and the Corps of Discovery on the Yellowstone

By editor

Livingston, Park County, Montana

On a midsummer day, July 15, 1806, Captain William Clark and a small detachment from the Corps of Discovery entered the valley of the Yellowstone River, near what is today Livingston, Montana. This moment marked a critical chapter in the expedition’s return from the Pacific coast. Clark had parted ways with Meriwether Lewis at Travelers’ Rest, near present-day Missoula, setting off with a purpose both geographic and scientific -- to explore the Yellowstone River and its environs, while Lewis took a separate course along the Marias River to the north.

The Yellowstone, a mighty tributary of the Missouri, courses eastward through a landscape carved from the ancient sediments of the Cretaceous and Tertiary periods. Clark’s party descended the river by canoe and horseback, threading their way through the towering sandstone cliffs and rolling plains that had been shaped over millions of years by tectonic uplift and the relentless flow of water. This section of the river valley offered a profusion of natural riches, and Clark’s journals brim with his keen observations of the terrain’s flora and fauna.

Clark’s capacity for mapmaking had earned him a reputation among the expedition leaders, yet the Yellowstone portion of his records reveals something beyond technical skill: a lively engagement with the world around him. On July 24, 1806, he wrote with a mixture of awe and practical concern: “Saw emenc number of Deer Elk and buffalow on the banks. Some beaver...for me to mention or give an estimate of the different Species of wild animals on this river particularly Buffalow, Elk Antelopes & Wolves would be increditable. I shall therefore be silent on the Subject further.” This declaration of silence was short-lived.

The wildlife along the Yellowstone was astonishing in its abundance. The plains near the riverbanks teemed with bison herds, elk, pronghorn antelope, wolves, and myriad birds. Clark’s journal entry from August 1, 1806, captures a vivid scene that unfolds before his eyes: “at 2 P.M. I was obliged to land to let the Buffalow Cross over. not withstanding an island of half a mile in width over which this gangue of Buffalow had to pass and the Chanel of the river on each Side nearly ¼ of a mile in width, this gangue of Buffalow was entirely across and as thick as they could Swim.” The image of these massive beasts, known scientifically as Bison bison, moving en masse across the Yellowstone’s channels reveals the vitality of this ecosystem before the drastic changes wrought by later settlement and industry.

The river itself flows through sedimentary formations deposited during the late Cretaceous period, approximately 70 to 80 million years ago. Sandstones and shales, sculpted by the persistent currents, form cliffs and buttes that rise abruptly from the valley floor. One such formation captured Clark’s attention and became a landmark of the expedition: a sandstone pillar that he named “Pompey’s Tower” on July 25, 1806, in honor of Sacagawea’s young son, Jean Baptiste Charbonneau, whom Clark affectionately called “Pompey.” This inscribed pillar remains the only physical mark left by the Corps of Discovery still visible on the landscape today, now known as Pompeys Pillar.

The significance of this site extends beyond the inscription. Pompeys Pillar rises some 150 feet above the Yellowstone River, its stratified layers revealing the slow processes of sediment deposition and lithification. The pillar’s presence offered a natural vantage point to survey the surrounding plain, a place where one could contemplate the vastness of the region’s geological history and the living world it sustained.

Clark’s writings display a scientific curiosity that matches his practical observations. He noted the presence of “antelops, wolves, pigions, Dovs, Hawks, ravins, Crows, larks, Sparrows, Eagles & ba,” a catalog of avian life reflective of the diverse habitats along the river corridor, from riparian woodlands to open grasslands. The abundance of game animals provided not only sustenance but also materials for the expedition’s survival -- skins for clothing and shelter, bones for tools, and sinews for cordage.

This profusion of wildlife, so richly detailed in Clark’s journal, contrasts sharply with the landscape’s later history. The bighorn sheep referenced by Clark, sometimes called Audubon’s race, have vanished from these plains. Yet, thanks to conservation efforts in the 20th and 21st centuries, the Yellowstone River valley continues to support diverse populations of fish and wildlife. Great blue herons still nest in rookeries along the river, white-tailed deer emerge from cottonwood groves, and the river itself runs free, a rare and precious condition in the American West.

Clark’s journey along the Yellowstone culminated at the confluence with the Missouri River on August 3, 1806. Here he paused to await Lewis. The two captains reunited on August 12, 1806, at the mouth of the Yellowstone, and together completed the last leg of the expedition, descending the Missouri River to St. Louis. Their journey had covered more than 8,000 miles over more than two years, producing maps and natural histories that would forever alter the understanding of the continent’s interior.

Reflecting on their expedition, Clark once remarked, “The country is as fine as it is extensive, and the abundance of game is truly astonishing” -- a statement that captures both the grandeur and the promise of the Yellowstone valley as it appeared to those first American explorers.

It is worth noting that the Corps of Discovery’s passage through the Yellowstone basin was not merely a European-American encounter with wilderness. Indigenous peoples had long known the region intimately, shaping the land and its resources in ways often unrecorded by the expedition’s journals. The richness of the wildlife and the river’s course had sustained native tribes for generations, and Sacagawea, herself a Shoshone woman, served as an indispensable guide and interpreter, bridging cultures and landscapes.

Today, standing at Pompeys Pillar or tracing the Yellowstone’s winding path, one can appreciate the precision and wonder with which Clark recorded this landscape. His journals provide more than a historical account; they offer a detailed snapshot of a living environment, a river valley at the height of its natural abundance.

See also

• Captain Clark and the Corps of Discovery on the Yellowstone at Livingston, Park County
• First Lewis and Clark Trail Marker at Livingston, Park County
• Legacy of Lewis and Clark: Opening the Yellowstone Corridor at Livingston, Park County