At one time, shortly after it opened, the speed limit on the Kansas Turnpike was "Reasonable & Proper". You could drive as fast as traffic and your ability to maintain control would let you.
That's how one could get from Wichita to K.C. in, say, two hours...back in the time.
I wish I was around for that :(
I’ve never been able to drive on a road with no limit. There are plenty of parts on the turnpike where you can easily drive 90 or more. Highly maintained, smooth, high banked turns.