Cite

[Outline Map of the United States] / engraved and printed by the U.S. Geological Survey.

MLA

[Outline Map of the United States] / Engraved and Printed by the U.S. Geological Survey. Bureau of the Census, 1920. https://collections.library.yale.edu/catalog/15827372.

APA, 6th edition

[Outline Map of the United States] / engraved and printed by the U.S. Geological Survey. (1920). [Maps]. Bureau of the Census, https://collections.library.yale.edu/catalog/15827372.