I love this time-lapse animation of all the county and state-level boundary changes in United States history.  Would you like to see this in greater detail?  Would you want to download the data and create your own visualization of this?  The Atlas of Historical County Boundaries has all of this data as GIS shapefiles, Google Earth KMZ files and PDFs for the whole country as well as for each individual state.  This project sponsored by The Newberry and the National Endowment for the Humanities has tremendous potential for use in the classroom for history and geography teachers alike.  

Tags: historical, USA, borders, time lapse, mapping, edtech.