Meriwether Lewis (Lenny) and William Clark (Carl) are assigned to explore the West by President Thomas Jefferson (Mayor Quimby). They meet a tribe of Native Americans, whose chief (Homer) offers them the guidance of his daughter, Sacagawea (Lisa), whose name means, "Little know-it-all who will not shut her maizehole." They are accompanied by her husband (Milhouse), until he is slaughtered by Sacagawea's brother (Bart).