U.S. News Map is a great resource produced by Georgia Tech and the University of Georgia. The U.S. New Map is an archive of American newspapers printed between 1836 and 1925. You can search the archive by entering a keyword or phrase. The results of your search will be displayed on an interactive map. Click on any of the markers on the map and you'll be shown a list of newspaper articles related to your search term. Click on a listed article to read it on the Library of Congress' Chronicling America website.
Applications for Education
The U.S. News Map has a neat playback feature that you can use to see the frequency with which a term or topic appeared in newspapers between 1836 and 1925. That playback feature could be a nice way to show students developments in technology. For example, search the term "telephone" and you'll see peaks and valleys in the frequency with which articles were written about telephones.
H/T to Google Maps Mania and Larry Ferlazzo.