For instance you can go to the website. Ask for directions from the city where you are starting and pick one you think you might go to. It'll give you a pin on the map for the second city. You can drag PIN B to other places to see how far it would be if you pick a different city.
At a rough guess depending on where you are in Kansas. Hit St Louis the first day. Indianapolis the second. Maybe Pittsburgh the third and Washington on the fourth. This assumes you want to stop in big towns so you can sightsee just a bit.