Final answer:
Sacagawea was the name of the French fur trapper's wife who was valuable to the Lewis and Clark expedition as an interpreter and diplomat.
Step-by-step explanation:
The French fur trapper's wife who proved extremely valuable in guiding and assisting the Lewis and Clark expedition was named Sacagawea. During the winter of 1804-1805, the expedition encountered Sacagawea and her husband, Toussaint Charbonneau, in a Mandan village, which is in present-day North Dakota.
Sacagawea, who had been kidnapped and sold to Charbonneau, who made her his wife, was of great assistance to the expedition as an interpreter and diplomat, particularly with the Shoshone people. Though not the guide of the party, her presence with her infant child suggested to various groups that the expedition was not a war party, which helped to provide a peaceful interaction.