Huh! And today I am linked on Facebook to a lovely page that shows factoids in maps. I have verified _none_ of the factoids but some seem relevant to this - the map of rivers in the US, the map of vegetation in the US, the map of rivers that feed into the Mississippi.... Some are just fascinating to look at. http://twistedsifter.com/2013/08/maps-that-will-help-you-make-sense-of-the-world/ - again, haven't fact-checked or even source-checked their data.