Lewis and Clark Geography: Rivers, Passes, and Route Maps - Yenra

Trace rivers first, then the crossings between them

Open the National Park Service trail maps and locate the Missouri River, the Rocky Mountains, and the Columbia River system. For the westward journey, trace the Missouri upstream, identify the overland passages through the mountains, and then follow the Clearwater, Snake, and Columbia downstream toward the Pacific.

A drainage divide separates water flowing toward different outlets. Crossing it changes the watershed, but finding a practical route still depends on valleys, passes, seasonal conditions, food, and local knowledge. The route across the mountains was a sequence of decisions, with different parties sometimes scouting separately.

The NPS expedition site chronology places Lemhi Pass in August 1805 and the Lolo Trail and Weippe Prairie in September. These are distinct parts of the crossing. Use the route line and the dated account together; a pass name alone leaves much of the journey unexplained.

On the return journey, look for branches and alternative routes before assuming the party simply retraced every westward step. A modern overview can combine different years and parties into one display. Its legend should tell you which is which.

Put Indigenous places and knowledge on the map

The expedition traveled through inhabited, named, and connected landscapes. At Great Falls, the NPS portage account explains that Mandan people had described the falls to Lewis and Clark. In the Bitterroots, the Lolo Trail had long been used by the nimíipuu, or Nez Perce. These routes and descriptions were geographic knowledge the expedition relied on.

The Nez Perce National Historical Park account describes assistance to the expedition in 1805 and its return in 1806. Read that alongside the Nez Perce Tribe’s own history, which describes Nimiipuu lands, seasonal movement for fishing, hunting, and trade, and the continuing place of traditional ways in tribal culture.

For a classroom map, add the relevant nations and places with their sources instead of leaving the area around the expedition line blank. Keep historical homelands, modern reservations, and present state boundaries as separately identified layers. They describe different kinds of geography and different periods.

Read historical maps and visitor maps for their purposes

An expedition sketch records what its maker chose to observe and communicate. A modern historic-trail map interprets the journey using later geographic knowledge. An auto-tour map organizes present roads and visitor sites. Each can help, provided its date, purpose, and legend stay attached.

The NPS maps page offers a brochure map and an interactive atlas. For original written observations, use the University of Nebraska–Lincoln’s Journals of the Lewis and Clark Expedition. Record the writer and entry date, then distinguish the historical entry from an editor’s explanatory note. Spelling, place names, estimated distances, and interpretations may differ from modern usage.

When aligning an old sketch with a modern map, begin with recognizable junctions and landforms. Compare orientation and scale. A rough historical drawing may preserve an important relationship between places while its distances or angles differ from a surveyed map.

Compare the Great Falls portage

1. Open the NPS Portage Route page, which includes William Clark’s map. Identify the river and the route around the falls.
2. Find the same area on the modern trail atlas. Mark the beginning and end of the overland section, keeping roads separate from the historic line.
3. Explain the transport problem. The NPS describes an approximately 18-mile portage: moving boats and supplies over land bypassed a sequence of waterfalls.
4. Write down one feature visible in both maps and one question the maps alone leave open. Resolve the latter with a dated journal entry or a sourced site account.

A useful conclusion connects terrain to a decision: “The river linked the camps, but the falls required an overland transfer.” Add whose account supports the explanation and how the location was identified. Use the route-comparison notes to repeat the exercise at another stage.