Final answer:
Sacagawea was the Native American woman who assisted the Lewis and Clark expedition as an interpreter and diplomat, rather than as a guide, due to her being kidnapped in childhood and thus not likely remembering her native land.
Step-by-step explanation:
The Native American woman who served as an interpreter and diplomat for the Lewis and Clark expedition was Sacagawea. Despite the idealized image of Sacagawea guiding the explorers through the Montana wilderness, in reality, she was a teenager at the time and did not serve as a guide, as she had been kidnapped as a child and was unlikely to remember her native land in detail. She was invaluable to the expedition, especially as an interpreter to the Shoshone people and as proof to other Native groups that the expedition was not a war party, due to her presence with a newborn son.
Sacagawea was kidnapped and sold to a French fur trapper named Toussaint Charbonneau, who took her as his wife. Charbonneau knew the land better and joined the Lewis and Clark expedition in the spring of 1805 as a guide and interpreter, with Sacagawea and their son in tow. Sacagawea's abilities helped to ensure peaceful interactions with the Native tribes the expedition encountered, and her presence helped to smooth diplomatic relations