The NU Library's Map Collection (part of Govinfo - location) was established circa 1947 as an official depository for the US Army Map Service. Most maps in the library were also centralized and housed in the collection.
Maps published before 1923 and maps published by the U.S. Government are in the public domain. Many of them can be found on the web. Here are our recommended websites to locate maps online!
Perry-Castañeda Library Map Collection - Online Maps
This library links to online maps available on the web and also scanned maps from its map collection. The best location to start your search.
David Rumsey Map Collection
The David Rumsey Historical Map Collection has over 14,800 maps online. The collection focuses on rare 18th and 19th century North and South America maps and other cartographic materials, but historic maps of the World, Europe, Asia and Africa are also represented. Maps can be downloaded in high resolution (but in MrSID format - requires a special viewer/add-on)
Congress Map Collections
American Memory Map Collections of the Library of Congress focuses on the United States, but historic maps of other countries are also included. Images are also available for downloading.
Map History : Images of Early Maps on the Web
The most comprehensive listing of historical maps websites, comprising over 1,200 annotated links.
Alabama Maps : by the University of Alabama
Similar to the Perry-Castaneda Library website (above) with more focus on historic maps. One major shortcoming is that images are for viewing only, not available for downloading.
Good to find thematic maps.
USGS Store by US Geological Survey
You can buy or download maps of the world and US from this USGS website. Topographic maps are probably the most popular product.