Government Shut down hasn't hit this site .... yet

A neat site to see old  USGS Topographic maps is found here.  For the most part the topo part (landforms) doesn't change that much, with the exception of mining and excavations from human activities.  What does change are the human elements like roads and such. 

Should the government shutdown shutdown this site, you can also visit this one.  Sponsored by our GIS friends at ESRI. 

Finally, while not "served" UNH has this website for you to download maps.