MLA

A New County Map of Pennsylvania and Adjoining States Showing the Route of the Rail Roads, &c. R.L. Barnes, no. 7 Hart's building, Sixth Street, above Chestnut, 1857. https://collections.library.yale.edu/catalog/15790131.

APA, 6th edition

A new county map of Pennsylvania and adjoining states showing the route of the rail roads, &c. (1857). [Maps]. R.L. Barnes, no. 7 Hart's building, Sixth Street, above Chestnut, https://collections.library.yale.edu/catalog/15790131.