There are no towns halfway between a single place.
halfway point between portsmouth nh and palm beach fl
Lavonia, Georgia, is halfway between those two towns.
Roseau and Portsmouth
Edinburgh to Maidstone is 420 miles, so halfway would be somewhere around Leeds.
Parkton, MD
Assuming you mean what town is halfway between Denver and Galveston. A small town named Childress is halfway, but the closest larger towns are Amarillo or Wichita Falls
Halfway between Louisville, KY, and Portsmouth, NH, is approximately around the area of State College, Pennsylvania. This location is roughly equidistant from both cities and offers a mix of urban and rural environments. It's a convenient meeting point along the route connecting the two locations.
There aren't many towns on that whole stretch of I-5. Wasco is the closest to halfway.
The halfway point between Portsmouth, VA, and Lumberton, NC, is around the area near Fayetteville, NC. Specifically, you could consider taking Exit 49 off I-95, which is near Hope Mills. This exit is approximately midway between the two locations and provides convenient access to services and amenities.
New England, ND
Longview TX or Marshall TX
Harrisonburg and Staunton, Virginia