Cite

Southwestern Colorado [cartographic material] / U.S. Geographical Surveys West of the 100th Meridian.

MLA

Geographical Surveys West of the 100th Meridian (U.S.). Southwestern Colorado [cartographic material] / U.S. Geographical Surveys West of the 100th Meridian.. BRBL_00587. [approximately 1876]. https://collections.library.yale.edu/catalog/15824425.

APA, 6th edition

Geographical Surveys West of the 100th Meridian (U.S.). (["BRBL_00587"])([approximately 1876])[Southwestern Colorado [cartographic material] / U.S. Geographical Surveys West of the 100th Meridian.]. https://collections.library.yale.edu/catalog/15824425.