Most of the photos on this site were extracted from reference images (high-resolution tiffs, 20 to 200 megabytes in size) from the Library of Congress research archive. (To query the database click here.) Many were digitized by LOC contractors using a Sinar studio back. They are adjusted by your webmaster for contrast and color in Photoshop before being downsized and turned into the jpegs you see here.
The full-size version of this is a kind of portal to the past. "May 1864. Fredericksburg, Virginia. Cooking tent of the U.S. Sanitary Commission." Photograph from the main Eastern theater of war, Grant's Wilderness Campaign, May-June 1864. Wet plate glass negative by James Gardner. View full size.