Mickey D's in the USA
If you needed any more visualization of how much denser the US is east of the Mississippi than west, check out the distribution of McDonald's restaurants in the lower 48 at http://strangemaps.wordpress.com/. The moral of the story is that if you're prone to Big Mac attacks, don't find yourself at N 45.45955 W 101.91356 in South Dakota: it's 145 miles to the nearest Golden Arches.
PS Speaking of retail juggernauts, here's a very cool map of Walmart openings in the lower 48. I love how the store openings are depicted as toxic green bubbles popping up all over the place. This depiction really highlights how Walmart went absolutely nuts in the mid-80's and again in the mid-90's.