Preparation and planning for the Lewis and Clark Expedition happened in the east. Meriwether Lewis travelled the Ohio River from Pittsburgh, Pennsylvania to its mouth in Cairo, Illinois. Along the way, he collected supplies and prepared for the expedition. Lewis joined with William Clark at the Falls of the Ohio where they recruited the first members of the Corp of Discovery and then departed for the west. Eastern Legacy: The Lewis and Clark Expedition Begins… describes the many sites travelled by Lewis and Clark along and near the Ohio River that can still be seen and visited today.