This map of the Louisiana Territory and North America dates to 1804, the same year the Lewis & Clark Expedition set out westward. It was part of a general reference atlas published in London. This helps us to understand how Jefferson and other educated people of the time had very limited knowledge of the West’s geography — of much beyond the Mississippi River. Spanish, French, and British explorers and fur traders had some presence in the vast Louisiana Territory, but in 1804 it was still land primarily occupied by Native Americans. The map reflects this “blank” about the West in the minds of Europeans and Americans.
Compare this to a map of the present United States, showing natural features such as mountain ranges, rivers, and coastline. What differences do you notice between the two — both in level of detail, and how the West (from the Mississippi River to the Pacific Ocean) is depicted?
Which major rivers, lakes, and other features do you recognize on this 1804 map? Which are missing? (For example, the Great Lakes are visible: Lake Michigan and Lake Superior. But are the major rivers such as the Missouri and the Mississippi accurately depicted? What about the Rocky Mountains, and other ranges such as the Sierra Nevada or the Cascades?) What might this map show about geographical knowledge before and after Lewis and Clark?
As indicated in the student section, the best way for students to understand this map — and how scant Americans’ geographical knowledge of the West was at the time of the Louisiana Purchase — is to compare it to a modern US map. Encourage students to look for major natural features (the Rocky Mountains; the Missouri and Columbia rivers, both of which Lewis and Clark traveled), which are absent or inaccurately depicted on this 1804 map. Related to this, Jefferson believed some rather wild things about the West before Lewis and Clark set out. Although a very learned man, who at the time possessed the best library in the world on North American geography, natural history, and Native American cultures, Jefferson thought that prehistoric animals such as the wooly mammoth and giant ground sloth might still be found along the Upper Missouri River. He also supposed that a mountain of pure salt rose somewhere beyond the Great Plains, and that the Blue Ridge Mountains of Virginia might be the highest on the continent.
Key features to notice about this 1804 map are: First, the Rocky Mountains are rendered as a narrow spine of mountains, not the complex, wide group of ranges that Lewis and Clark had to cross. This also hints that the Rockies might be an easy portage between river systems on either side, which is what Jefferson believed — see Source 3, his instructions to Lewis. Second, there is almost no detail about the Pacific coast, or anything west of the Rocky Mountains. Many explorers — US, British, Spanish, and others — had visited the Pacific coast by 1804, but they did not explore inland much if at all. (In 1792, American explorer Robert Gray sailed a short distance up the Columbia River from the Pacific Ocean. British mariner George Vancouver explored the coast of Oregon, Washington, and British Columbia in 1792 – 1793, but did not enter the Columbia River.) Students can compare this map with Source 10, the map by William Clark published in 1814. Lewis and Clark vastly increased Americans’ understanding of Western geography through their careful observations — including knowledge gleaned from Native American peoples they met — and Clark’s fine cartography.
This is a hand-drawn, black-and-white map dating to 1804, entitled “Louisiana,” depicting the western portion of North America. It runs from Hudson Bay (in the northeast of Canada) south to the Gulf of Mexico, and also shows the northern portion of present-day Mexico. The broad outlines of the continent and many major natural features are recognizable: Lakes Michigan and Superior, the Mississippi River, and the outlines of the Pacific coast and the Baja California peninsula. But the map also reflects the sketchy geographical knowledge of the time. For example, the Rocky Mountains are shown as a narrow spine of mountains very close to the Pacific coast, and there are no features shown west of the Rockies or along the Pacific coast of what is today California, Oregon, and Washington.