MLA

Commission, Oregon State Highway. Map of State of Oregon Showing Main Traveled Roads / Oregon State Highway Commission. Oregon State Highway Commission, 1921. https://collections.library.yale.edu/catalog/15952282.

APA, 6th edition

Commission, O. S. H. (1921). Map of state of Oregon showing main traveled roads / Oregon State Highway Commission. [Road maps]. Oregon State Highway Commission, https://collections.library.yale.edu/catalog/15952282.