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Primary
US National Archives

Nara: Charters of Freedom: Westward Expansion: Louisiana Purchase

For Students 9th - 10th
Primary source material and informational text on the Louisiana Purchase.
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Website
Other

The Smithsonian: Lewis & Clark: Mapping the West

For Students 9th - 10th
The Smithsonian's EdGate project provides this illustrated narrative site that explores the mapping of the American West accomplished by the 1804-06 Lewis and Clark expedition.