Cite

Post route map of the state of Oregon and territory of Washington / designed and constructed under the orders of D.M. Key [by] W.L. Nicholson.

MLA

Dept, United States. Post Office. Post Route Map of the State of Oregon and Territory of Washington / Designed and Constructed under the Orders of D.M. Key [by] W.L. Nicholson. s.n., 19AD. https://collections.library.yale.edu/catalog/15821622.

APA, 6th edition

Dept, U. S. P. O. (19 C.E.). Post route map of the state of Oregon and territory of Washington / designed and constructed under the orders of D.M. Key [by] W.L. Nicholson. [Maps]. s.n., https://collections.library.yale.edu/catalog/15821622.