Welcome to RTA, and an early welcome to Missouri!
My husband and I traveled to DC about 3 years ago and came to central MO by the following route (click here to be taken to our description of this route): We took one route over to I-81, then took I-64 almost the entire way to St Louis. This avoided a LOT of cities, as the ones along I-64 are smaller cities. Maybe the biggest city along I-64 is Louisville. From St Louis, you'd get on I-44 and take that all the way in to Springfield. (We took I-70 from St Louis as we were headed into Columbia, MO.)
There were two reasons we chose I-64. First, we'd driven most of the length of I-70 over the years, a few times. I wanted to see something else! We hadn't traveled through WV or KY very much, over the years, and this was our opportunity. Now I want to go back! The other reason was to see if there was less commercial truck traffic. That answer was a big LOTS LESS.
Again, welcome to MO. We just moved here to MO (Click here for the road trip report) over the summer (from SoCal) and live about 90 miles from Springfield. They *just* opened a Costco there (hubby and I still have our membership) and there's a lot of other things that Springfield has to offer.
Donna