The halfway point between Greensboro North Carolina and Fairfax Virginia is Pittsburgh.
Greensboro, NC is about halfway but it can depend on the route you take
Greensboro
Kernersville
Huntsville, Mississippi
Alabaster Al
Atlanta, GA is the halfway point between Greensboro, NC and Destin, FL.
Perry, GA on I-75 (halfway point of 358 miles)
Christiansburg, Virginia
Carbonton, NC
The halfway point between Greensboro, NC and Charlotte, NC is Salisbury, NC
Sailsbury NC is pretty close.