Final answer:
Sacagawea accompanied Lewis and Clark as the American Indian interpreter on their journey of exploration.
Step-by-step explanation:
The American Indian interpreter who accompanied Lewis and Clark on their journey of exploration was Sacagawea. She played a crucial role as an interpreter and diplomat to the Shoshone people. Sacagawea and her husband, a French fur trapper named Toussaint Charbonneau, joined the expedition as guides and interpreters. They brought their newborn son along, and Sacagawea's presence helped convey the expedition's peaceful intentions.