Allan Pinkerton on horseback at Antietam, Md.
<bdi><a href="https://en.wikipedia.org/wiki/en:Alexander_Gardner_(photographer)" class="extiw" title="w:en:Alexander Gardner (photographer)"><span title="Scottish photographer (1821–1882)">Alexander Gardner</span></a>
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1862-09
<bdi><a href="https://en.wikipedia.org/wiki/en:Library_of_Congress" class="extiw" title="w:en:Library of Congress"><span title="(de facto) national library of the United States of America">Library of Congress</span></a>
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