My guess and that is Eleanor Roosevelt. A very bad choice but I bet she is the one.
I would prefer Sacajawea. She really did become almost indispensable to the Lewis and Clark expedition. She also preferred to live with White People and moved to St. Louis. She died of fever while still young.
Lewis and Clark was an interesting endeavor, but in the overall scheme of things, was it really essential to the nation?
Considering Washington, Lincoln, Hamilton, Jackson, Grant and Franklin, what business does Sacajawea have being put next to this Pantheon? Not even Lewis or Clark should be regarded as their peer.