Plaster has long been used to replicate works of art, especially sculptures and reliefs. Plaster guarantees a mechanically objective, one-to-one copy, which allows for an equally objective comparison, classification, and formal analysis of the original. By the late 19th century, plaster casts had become essential teaching tools at universities across the United States. This essay and its accompanying illustrations detail the long history of the plaster cast collection at the University of Missouri.