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Sacagawea's son, Jean Baptiste Charbonneau—nicknamed Pompy by Clark—is born with assistance from Lewis.
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Lewis and Clark send a shipment of artifacts and specimens to President Jefferson; the "Permanent Party" heads west.
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The Corps marvels at the abundance of game; they kill their first grizzly bear near the Yellowstone River in Montana
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One of their boats nearly overturns and Lewis credits Sacagawea with saving their most important possessions
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The Corps reaches the White Cliffs region of the Missouri River
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The Corps reaches an unknown fork in the Missouri and must determine which branch to choose.
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Lewis reaches the Great Falls of the Missouri—five massive cascades around which the men must carry all of their gear, including the canoes.
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The expedition reaches the Three Forks of the Missouri which they name the Jefferson, Gallatin, and Madison in honor of the President, Secretary of the Treasury, and Secretary of State