Returning to the Plains: Clark on the Yellowstone

By editor

Glendive, Dawson County, Montana

In the late summer of 1806, Captain William Clark once again found himself upon the broad plains of what we now call eastern Montana. After months of traversing the rugged and towering Rocky Mountains, he descended to the gentler contours of the Yellowstone River valley, a landscape both familiar and new. Clark’s journal entries from July 28 through August 3 reveal a man keenly observing the land’s natural features and its abundant life, even as he contended with the practical difficulties of river travel and intermittent storms.

On July 28, 1806, Clark set out at dawn, “glideing down this Smooth Stream passing maney Isld,” a phrase that captures the tranquil flow of the Yellowstone as it meanders eastward. The river here, roughly 150 miles upstream from its confluence with the Missouri, carves a valley through sedimentary hills laid down during the late Cretaceous period, some 70 million years past. These rolling hills, composed largely of sandstone and shale, harbor seams of coal--an observation Clark noted the very next day.

July 29 brings a vivid record of the natural wealth along the riverbanks: “in the fore part of the day, I saw great numbers of Buffalow on the banks, … great quantities of Coal in all the hills I passed this day. … Beaver is very plenty on this part of the Rochejhone.” The buffalo, or American bison (Bison bison), ranged in vast herds across the plains, their presence a signal of the rich grazing lands. The coal seams Clark mentions formed from ancient plant material compacted and transformed over millions of years, a resource that would much later fuel the industrial growth of this region.

The beaver (Castor canadensis), too, thrived here, their dams altering stream flow and creating wetland habitats that supported a variety of birds and fish. The riverbanks were alive with mammals and birds, and Clark’s keen eye did not miss a single detail.

The following day, July 30, Clark writes of “the first appearance of Birnt hills which I have Seen on this river.” These “birnt hills” refer to the exposed, darkened rock formations that bear traces of ancient volcanic activity--remnants of the Yellowstone Plateau’s fiery past. Though the volcanic caldera that defines modern Yellowstone National Park lies some distance upstream, the geological forces that shaped this entire region left their mark in these blackened outcrops.

By August 1, the weather shifted. Clark describes “Showers of rain repeetedly all day... My Situation a very disagreeable one. in an open Canoe wet and without a possibility of keeping my Self dry.” The open canoe, a dugout crafted by Native Americans, offered no shelter from the persistent rain. The damp and chill would have tested even the hardiest of explorers. At 2 P.M., Clark was forced to “land to let the Buffalow Cross over … the river was crouded with those animals for 1/2 an hour.” To witness such a congregation of bison in the river is to imagine the slow, powerful movement of hundreds of beasts, their dark forms bobbing and snorting amid the current. The buffalo crossed in family groups, swimming from one riverbank to the other, an essential part of their seasonal migrations.

The next day, August 2, brought a more dramatic encounter. Clark recounts: “about 8 A.M. this morning a Bear of the large vicious Species being on a Sand bar raised himself up on his hind feet and looked at us as we passed down near the middle of the river. he plunged into the water and Swam towards us, either from a disposition to attack't or from the Cent of the meat which was in the Canoes. we Shot him with three balls and he returned to Shore badly wounded.” This bear was likely the grizzly (Ursus arctos horribilis), a species revered and feared for its size and ferocity. The bear’s approach and subsequent retreat illustrate the tense relationship between man and beast on these untamed waters.

Clark’s journal entry for August 3 reveals the toll of a relentless environment: “last night the Musquetors was so troublesom that no one of the party Selpt half the night. ... at 8. A.M. I arived at the Junction of the Rochejhone with the Missouri, and formed my Camp ...” The mosquitoes, emerging in clouds from the wet river valley, made rest difficult. Yet the junction itself was a significant waypoint, where the Yellowstone meets the Missouri, the great artery of western water travel.

Clark also notes, “The Rochejhone or Yellow Stone river is large and navagable with but fiew obstructions ... The Country through which it passes from those Mounts to its junction is Generaly fertile and well Timbered.” His observation underscores the fertile floodplain that would support both native peoples and wildlife for millennia. The river, wide and steady, offered a navigable route through a landscape of rolling hills, cottonwoods, and prairies.

The Yellowstone’s course through this valley is tied to ancient geological processes. The river flows over sedimentary rocks deposited in inland seas during the Cretaceous era, sculpted by glacial activity during the Pleistocene ice ages. The hills Clark described are capped by loess--windblown silt that blankets the plains, nourishing grasses that sustain the bison herds.

Clark’s journey on these waters was more than a passage through space; it was a survey of the natural riches that defined the northern plains. His detailed notes, written with the precision of a naturalist, convey a world teeming with life and shaped by deep time.

Reflecting on the entire expedition, Clark once remarked, “I considered this the most beautiful river I had ever seen.” This declaration, recorded in a letter to President Thomas Jefferson, captures the awe inspired by the Yellowstone’s clear waters and fertile banks. It also foreshadows the river’s central place in the unfolding story of American exploration and settlement.

Today, the same Yellowstone River flows past Glendive, coursing through the Dawson County landscape much as it did in 1806. The hills and valleys remain, and with them, the echoes of the wildlife that Clark observed--pronghorn antelope, mule deer, and, in smaller numbers, the bison that once dominated these plains.

Clark’s journal entries offer us a window into a moment when the natural world was still largely untouched by large-scale human alteration. His observations on geology, flora, and fauna provide a precise record that enriches our understanding of this remarkable region.

As I consider the detail and care with which Clark recorded his encounters, I am reminded that the plains and river valleys of Montana hold stories written in stone and river water, stories that continue to unfold for those who choose to look deeply.

See also

• Returning to the Plains at Glendive, Dawson County
• Evidence of the Expedition at Glendive, Dawson County
• [Lewis and Clark in Missouri River Country](/historic-markers/le