That distance is 280 road miles, making Oklahoma City at 140 miles a perfect locale for dining or an overnight stay.
If you go south to Denver and cut across, the halfway point is Collyer, KS. If you go west to Kearney and turn south, the halfway point is Smith Center KS, which is about 15 miles away from the center of the contiguous US. There's a plaque there.
Atoka OK
One halfway point between Lawton, OK and Chicago, IL is Lincoln, MO.
Jackson, TN.
The I-35 and Highway 60 junction west of Ponca City, OK will be approximately halfway.
Elk City, OK
The halfway point between Tulsa, OK and Fort Campbell, KY falls in or around Mountain View, MO.
halfway point between ABQ, NM and San Antonio, Tx
Anadarko, OK ... just west-ish of Oklahoma City, OK
Hinton, OK
Louisville, KY?
Durant, OK