To get to a McDonald's in the lower 48 United States, it's never more than 145 miles by car. And the McFarthest Spot in the US is in South Dakota.
For maximum McSparseness, we look westward, towards the deepest, darkest holes in our map: the barren deserts of central Nevada, the arid hills of southeastern Oregon, the rugged wilderness of Idaho's Salmon River Mountains, and the conspicuous well of blackness on the high plains of northwestern South Dakota.
See also maximum Starbucks density and Starbucks center of gravity of Manhattan.
Update: The distribution of McDonald's in Australia is a bit more uneven. (thx, kit)
