If you decide to stay in Springfield into Sunday, the state fair has lots of great food vendors - we personally love Culler's fries or Vose corn dogs :) Of course, there are typical fair things to do here, riding rides, looking at the Butter Cow, etc.
If you are looking for a great brunch spot or dinner, this is your place to go! It is located in downtown Springfield, close to the State Capitol. They offer flat breads, horseshoes (which is a must in Springfield), or burgers. They have an extensive spirits menu with fun cocktails and a beer garden.