Captain Lewis was an army official. He was appointed by Thomas Jefferson as leader of the expedition. He was a cultured man and a scholar, with great knowledge about botany, geology, astronomy, and medicine. He did not have a very favorable view about the native americans, and he also owned slaves.
He was very interested in the journey, specially because it represented an opportunity to acquire scientific knowledge. He dedicated the winters to write extensive journals about the findings, and he also drew a lot of maps of the area.
Lewis Clark was appointed by Meriwether Lewis as second in command. He also was a man of culture and science. He had a more favorable view on native americans, and in later years, he became an advocate for the native american cause. He became governor of Missouri about a decade later.
Sacagawea was a woman belonging to the Shoshone tribe. He married a French-Canandian fur trapper, but not on her own will because she was sold to him. When Lewis and Clark met Sacagawea, she was giving birth. Captain Lewis had rattle snake oil, and gave it to Sacagawea, who was in great pain. She felt better and in exchanged, became a guide and an interpreter for Lewis and Clark.