Oh, one more thing. Lewis and Clark camped just south of Wood River (Camp Dubois) before starting up the Missouri River, just across the Mississippi from the camp. There were lots of things scheduled for the bi-centinial at the site, which is just off of Ill. Rt. 3.
You can connect here from the SIU campus on country roads too, just in case you are interested. I recommend county roads in this area because the main roads have no shoulders, and the drivers are, well, nuts! Besides the country roads are beautiful in fall.

Gus, riding east to west will give you strong head winds in most of the western states, combined with mountains you'll need to allow extra time. Just so you know, better to go west to east.
Good riding!