In a recent article in the print edition of Family Tree Magazine, Lisa Louise Cooke listed six very large online collections of maps. This list got me thinking and I decided visit a few of the sites and some others besides those in the magazine. The largest collection of maps listed was that of the National Library of Australia. However, the article claims that there are 300,000 maps in the collection, but the Website states that there are " Over 7225 items from the Map Collection are now accessible online. To review our progress read Maps digitisation - progress so far and Digitisation - overview." "The Maps digitisation - progress so far" article states that as of 30 June 2009 they had digitized 8,856 items, consisting of 16,775 images. Still a very valuable collection.
One small source for finding map collections is the Cartographic Information Center of the Louisiana State University, Department of Geography and Anthropology. This smaller site refers you to a much more extensive collection, the Perry-Castañeda Library Map Collection of the University of Texas Libraries. The links provided by this Website are extensive and way too long for this post.
One significant collection, although regional, is the Historic Maps Online of the University Library of the University of Illinois at Urbana-Champaign. One of the largest collections of maps in the world is in the New York Public Library. To quote their site, "Established in 1898, the Map Division today holds some 431,000 maps, 16,000 atlases and books about cartography. The collection is international in scope, and dates from the 16th century to the present, with a focus on cities, especially New York City. Computer mapping and Geographic Information Systems [GIS] are new programs of the Map Division. Six computer mapping workstations are located in the newly renovated Map Division for public use." The collection includes the online collection of over 1,000 maps of North America from the earliest printed portrayals to the close of the 19th century; multiple versions and editions allow for historical comparisons.
There are really an almost endless variety of maps and collections.