Parkton, MD
A city that is roughly halfway between Elizabethtown, PA, and Billings, MT, is approximately in the area of Green River, Wyoming. This location is situated along major highways, making it a practical meeting point between the two cities. Other nearby towns in that region could also serve as halfway points depending on the exact routes taken.
There are no towns halfway between a single place.
Lavonia, Georgia, is halfway between those two towns.
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
There aren't many towns on that whole stretch of I-5. Wasco is the closest to halfway.
New England, ND
Longview TX or Marshall TX
Harrisonburg and Staunton, Virginia
Philadelphia is the city that is halfway between Washington DC and Boston MA. New York and Baltimore are the other towns that are in between.
Timaru is closest town to halfway between the two towns. It is 167 km from Christchurch and 192 km from Dunedin .
Halfway between Pensacola, FL, and Killeen, TX, lies the town of Vicksburg, MS. Another option is Monroe, LA, which is also approximately equidistant between the two cities. These towns provide convenient stopping points along the route.
The most notable towns halfway between Biloxi and Atlanta are Greenville Alabama and Mongomery Alabama.