MLA
Erwin, W. L. Rapid Transit at Harper's Ferry [Hand Colored]. 1913. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 74. https://digital.library.emory.edu/purl/4644qrfj93-cor.
APA, 6th edition
Erwin, W. L. (1913). Rapid transit at Harper's Ferry [hand colored] (Box 74) [Photographic postcards]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/4644qrfj93-cor.
Chicago
Erwin, W. L. “Rapid Transit at Harper's Ferry [Hand Colored].” Photographic postcards. Robert Langmuir African American Photograph Collection, 1913. Box 74. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/4644qrfj93-cor.