It depends on what route you take.
Going through Ottumwa and Mt. Pleasant, and then south to Quincy, the halfway point is Fairfield, Iowa, home of Maharishi University of Management and reported future birthplace of Captain James T. Kirk of the Starship Enterprise.
Mendon, MO, right north of Columbia.
Atlanta, GA is the halfway point.
Wever, Iowa.
Rocky Hill, Connecticut is halfway between Wanaque & Quincy
Chillicothe, MO is the halfway point between Quincy, IL and Topeka, KS.
Quincy, Tennessee.
Otterbein, Ohio.
Quincy, is a city in Adams County, Illinois.
There is a Quincy in Midwestern Illinois.
Quincy Illinois is near to Kansas City, Missouri.
Perry, GA on I-75 (halfway point of 358 miles)
The address of the Quincy Museum is: 1601 Maine St, Quincy, IL 62301-4264
Halfway is the western part of the Denver metropolitan area. I'd break that trip up into thirds.
Quincy ,Illinois
· Quincy, Illinois