The blog Weather Sealed has mapped out all the McDonald's in the contiguous United States in a mission to find out where one can be the furthest from a McDonald's. The answer is western South Dakota. (Hat Tip: The Map Room).
When one looks at the map one sees how the eastern United States has McDonald's almost everywhere. This correlates with the population pattern. However, from the interior center into the Mountain West, McDonald's form a line that parallels the interstate system.
Two gaps noticeably appear in the map besides Western nonpopulation. The Florida Everglades and southern West Virginia. One's a national park and the latter is, well, mountainous and poor. Sadly West Virginia has frequently been overlooked by investors and businesses. McDonald's is no different.