The town that marks the exact halfway point is actually Mack, Colorado but a better choice might be Grand Junction, Colorado which is about 23 miles from the exact midpoint.
The halfway points are the points which mark the half distance covered by the flight. These lie in the mid of both the above mentioned places. These points change for different locations. Halfway points for the above mentioned places are - Columbus, Nebraska, which is northwest of Lincoln.
Cheyenne is the capital of Wyoming. Denver is the capital of Colorado. Lincoln is the capital of Nebraska.
Halfway is the western part of the Denver metropolitan area. I'd break that trip up into thirds.
Lake Valley, Oklahoma is halfway between Denver & Sulphur
denver
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
Mission, South Dakota is roughly halfway between Fargo, North Dakota and Denver, Colorado.
Denver, Colorado is about halfway.
Dawsonville, Missouri is your halfway point.
Amarillo, TX
Hays, KS is roughly the halfway point. You should be able to reach Hays, form Denver on one tank of gas. Hays to Columbia is doable, but it might get tight. Hays is roughly 340 miles from Denver. From Hays to Columbia is roughly 390 miles.
A rough estimate would be Amarillo, Texas.