Fascinating animation about the development of Wal-Mart in the US from 1965 (first store in Bentonville to the 3176th in 2007).
Click HERE to see the animation
It spreads like wildfire especially from the 1980's years. What's interesting is that you can see that Wal-Mart has developed his stores through logistics.
First build a warehouse then stores around to maximize transportation and supply chain costs.
Second golden rule, absolute priority to rural places before entering downtown (the legend says that it comes from Sam Walton spouse strongly attached to her rural roots).