Resource collection for independent study. Image detail from Library of Congress:

Portrait of a lone black woman in bonnet holding basket standing in front of the "slave pen" in Alexandria, Va., the firm of Price, Birch & Co., "Slave Dealers," in the background. (Marked "2300.")
Reproduction number: LC-DIG-cwpb-01474 (b&w copy scan of of left half of glass stereograph negative); LC-DIG-cwpb-01473 (b&w copy scan of right half of glass stereograph negative)
Call number: LC-B811-2300 (glass negative); LOT 4161-H (photographic print)