History of aerial photography
Fantastic slideshow here from Slate (or click the picture).
"Now, with the advent of satellite technology, we've become largely accustomed to the wonder of seeing the Earth from so distant a perch. But until fairly recently, encompassing images of the planet were a novelty that gave its residents an entirely new perspective on the planet. Here, in honor of Earth Day, is a slide-show history of aerial photography, as shot from a variety of vehicles. And pigeons."