The Keystone View Company was a major distributor of stereographic images, and was located in Meadville, Pennsylvania. From 1892 through 1963 Keystone produced and distributed both educational and comic/sentimental stereoviews, and stereoscopes. By 1905 it was the world's largest stereographic company. In 1963 Department A and the Education Departments were closed down, but Keystone continued to manufacture eye-training stereographic products as a subsidiary of Mast Development Company. In 1972 Mast closed the Meadville manufacturing site.