Collection comprises over 350,000 stereoscopic photographs and negatives that depict the
world between the late-nineteenth and mid-twentieth centuries. Firms represented in
Keystone-Mast include Keystone View Company, Underwood and Underwood, B.W. Kilburn, H.C.
White Company, Universal Photo Art Company (C.H. Graves), American Stereoscopic Company,
W.H. Rau, Berry, Kelley and Chadwick, and George Rose. The photographs are not stereo cards,
but contact prints from the original negatives, annotated by Keystone staff and