Came across a cool site on Gizmodo today and found it to be an incredible time waster for people who like surfing old topo maps.

A potentially great tool for researching airport history or finding long lost ones.

http://chrismahlke.github.io/explorer_dev/

Find a location, and click to create a point on the base map

From there you can see a timeline of dates for archived maps - 1973 in this case

And then go back to a much earlier and simpler time - 1937 perhaps