Most of the hotels I remember in Galesburg are located near the mall - there was a Fairfield and Comfort Inn as I recall. There was another property (Jumers?) located on an I-70 offramp on the north side of town. I stayed at all three about ten years ago, the first two were ok, the last one, eh, not so hot.
Downtown, there used to be a Ramada Inn that was on the roundabout on main street, just up from where the old Santa Fe station was. This would be a long walk, or short cab ride away.
FWIW, Enterprise used to have a car rental location right by the station. Not sure what the story is with rental pickups, they used to work with folks pretty well and the location was ideal. There is also a local Ford dealership that did rentals.
Good luck with your trip, it's a neat area, lots of history and nice scenery!