Not the midwest of further, but within your 14 hour drive time.

Natchez Trace Century Ride Sat May 4, 2019
https://runsignup.com/Race/MS/Ridgel...?remMeAttempt=
This was the first organized ride I ever rode and is still my favorite. Very good organization and support compared to the others I've done since. A good lunch after the ride and usually a pretty good dinner buffet or finger foods for the evening during the prize give-a-ways.

Or one I'm thinking about trying the week before for the first time.

Hattie Hundred Bike Ride Sat April 27, 2019
https://runsignup.com/Race/MS/Hattie...undredBikeRide
I've have ridden the Long Leaf Trace. It's 41 miles of paved railroad bed from the rails-to-trails projects, extending northwest of Hattiesburg MS to Prentiss MS. Being a former railroad there is nothing on it to call a hill.