The Horse Heaven Hills are located adjacent to the Yakima Valley in Eastern Washington State. Peaks range between 1400 and 1600 feet in height. Children being driven from the local metropolis of Sunnyside on the way to Prosser literally believe that these hills are where all the world's dead horses roam.
Pronouncing the towns in Eastern Washington creates interesting sounds: Toppenish, Wapato, Granger, Prosser, Grandview, Sunnyside, and Yakima to name a few.
A common childhood game takes place while being driven past some of the interestingly named towns. It consists of sibling A asking sibling B "What's the name of that town?" When they respond "Wapato" sibling A immediately stomps on the foot of sibling B.
Ouch.