Library of Congress Prints & Photographs Online Catalog
Reader Jim N pointed me to the incredible Library of Congress Prints & Photographs Online Catalog (PPOC). Included are a wealth of historical images, many of which can be downloaded as high resolution TIF files (some images have “no known restrictions on publication” and others do have restrictions). Old glass-plate images, daguerreotypes, etc are all online. Cool stuff, if you have the time for browsing.
From the US civil war era, glass plate negative