Lewis and Clark National Historic Trail

By editor

Loma, Chouteau County, Montana

The Lewis and Clark National Historic Trail traces the path of the Corps of Discovery, a journey begun in the spring of 1804 from Wood River, Illinois, winding nearly 4,000 miles west to the Pacific Ocean, and then retracing a similar path eastward by 1806. This monumental expedition covered close to 8,000 miles over two years and stands among the most ambitious ventures of exploration in North American history. In Montana, the trail follows the Missouri River corridor, threading through ancient geological formations carved by millennia of water and ice, passing the rugged spine of the Rocky Mountains, and descending the Columbia River system toward the ocean.

At the small settlement of Loma, where the Marias River joins the Missouri, the expedition confronted a critical geographical dilemma in June of 1805. Here, two rivers converge with deceptive similarity--the north fork, the Marias, and the south fork, the true Missouri. The captains, Meriwether Lewis and William Clark, faced the challenge of determining which channel led toward the river’s source and onward to the fabled Northwest Passage they sought. Their decision was no trivial matter. Choosing incorrectly would have sent them northward into the Canadian Rockies, away from their intended course and into foreign territory.

Most of the men, unfamiliar with the subtle differences in current and riverbed, initially favored the north fork. Yet Lewis and Clark, relying on careful observation and the guidance of their Native American companions, suspected the south fork was the main stem. They spent several days navigating and charting both branches, examining the banks, the flow, and the surrounding terrain. Finally, they resolved to pursue the south fork, a choice that proved correct. This river led them past the Great Falls--an extraordinary series of cascades and cataracts plunging nearly 600 feet in total--before reaching the headwaters near Three Forks, Montana. The captains recorded their findings meticulously; Clark wrote on June 12, 1805, “The river appears to run towards the South and West and is the main branch of the Missouri.”

The landscape hereabouts reveals the ancient history of the continent. The rocky cliffs and river terraces display layers of sedimentary rock from the Cretaceous period, roughly 70 to 100 million years old, overlain by glacial deposits from the last Ice Age. The Missouri River itself, a powerful agent of erosion, has sculpted deep valleys and exposed fossil-rich strata. Among the flora, stands of ponderosa pine (Pinus ponderosa), with their distinctive orange-brown bark, dominate the drier slopes, while cottonwoods (Populus deltoides) and willow (Salix spp.) flourish along the riverbanks. The air carries the scent of sagebrush (Artemisia tridentata) and the distant cry of the mountain bluebird (Sialia currucoides) cuts through the morning stillness.

The National Historic Trail was formally established in 1978, conceived to honor the 200th anniversary of the expedition and to protect the route’s natural and historical significance. Its administration falls primarily to the National Park Service, working in concert with the Bureau of Land Management, the Forest Service, and various state agencies. The trail corridor in Montana encompasses some of the most pristine and least altered landscapes along the entire route, preserving the environment much as Lewis and Clark would have encountered it two centuries ago.

The expedition’s journals provide abundant detail on the natural world they encountered. Lewis, who served as the expedition’s naturalist, documented scores of new species and geological features. He described the Great Falls region with particular awe: “The scene is truly sublime and grand beyond description.” His observations included the sighting of the grizzly bear (Ursus arctos horribilis), which he noted as “the largest and most ferocious animal we have yet seen.” Such descriptions reveal the expedition’s blend of scientific inquiry and survivalist pragmatism, as they sought to understand the land while navigating its challenges.

Moreover, the choice at Loma illustrates the critical role of careful observation and local knowledge in exploration. The captains' hesitation and thorough examination exemplify the empirical spirit that marked their journey. They did not rely simply on instinct or hearsay but measured the rivers’ depths, currents, and directions. Clark’s sketches of the river forks helped clarify their course, demonstrating an early form of field cartography that would influence the mapping of the American West.

The trail today invites reflection on the vast scale of the continent’s geological processes. The Missouri River, a lifeline for millennia, originates near the convergence of three streams at Three Forks, flowing eastward across the Great Plains before joining the Mississippi. Its waters carry sediments from the Rocky Mountains, depositing them in broad floodplains rich with biodiversity. Around Loma, the river’s meanders and oxbow lakes create habitats for species such as the white pelican (Pelecanus erythrorhynchos) and the elusive river otter (Lontra canadensis).

In traversing this landscape, one senses the slow persistence of natural forces. The exposures of Cretaceous shale and sandstone tell of seas long vanished, while glacial erratics scattered across the plains testify to the ice sheets that once advanced over this land. The Lewis and Clark National Historic Trail preserves not only the passage of men but also the ancient narrative embedded in stone and soil. The captains’ words remind us that every bend in the river and every ridge in the hills carries a story shaped by time.

Reflecting on their journey, William Clark once wrote, “The perseverance and fortitude required to complete this expedition are beyond ordinary measure.” Their determination, coupled with a keen eye for detail and an honest reckoning with nature’s vastness, forged a path into the unknown. The trail remains a corridor through history and geology alike, inviting us to witness the land as it was then and as it endures today.

See also

• Lewis and Clark National Historic Trail at Loma, Chouteau County
• Lewis and Clark National Historic Trail at Big Sandy, Chouteau County
• Land of Many Uses at Shonkin, Chouteau County