These projects take primary/historical data and represent it visually in new ways, in order to make patterns or trends visible or to facilitate new interpretations.
Please note: The data, the numbers, are generally primary, but the maps themselves are secondary, because they represent a particular manipulation or interpretation of the original data. Both can still be excellent sources to reference, but keep the difference in perspective.
Unknown author; Kurz & Allison, Art Publishers, Chicago, U.S.A. / Restored by Michel Vuijlsteke [Public domain], via Wikimedia Commons
Credit: This box of links was originally created by Northwest Michigan College Library
Ken Lund from Las Vegas, Nevada, USA [CC BY-SA 2.0], via Wikimedia Commons
Image from page 342 of "The photographic history of the Civil War : in ten volumes" (1911), via Flickr.
"Havoc," effects of a 32-pound shell from gun of Second Massachusetts Heavy Artillery. Confederate caisson and eight horses destroyed. Fredericksburg, May 3, 1863. Capt. Andrew J. Russell. Mathew Brady Collection. [Public domain], via Wikimedia Commons
Hospital scene behind the lines of Pickett's Charge, Gettysburg, Pa. Boston Public Library CC BY via Flickr
Kurz & Alison, "Battle of Stone River." Library of Congress [Public domain]