Stereographs, a quintessential form of 19th-century parlor entertainment, could be found in the majority of the era’s middle-class homes as a sign of civility, taste, education, and refinement. A unique visual medium, stereographs created a three-dimensional image when viewed with a stereoviewer. Subjects included landscape and city views, ethnographic views, images of historic sites, and scenes from sensational events. The entertaining photographs were sold through a variety of vendors, including photographers, stationers, dry and fancy goods stores, and door to door canvassers. Occasionally, they were also used for advertisement purposes. By the later 19th century stock publishing houses dominated the stereograph trade rather than the photographers of the works whose negatives and rights they purchased. Keystone View Company absorbed the other major publishing companies by the early 20th century and focused production on educational series designed for classroom use.