This large and very colorful thematic map is the third edition of a map first issued in 1872. The map identifies forts, watershed, major towns and more. The legend at lower left provides an explanatory key to the colors used to indicate nine distinct geological types, e.g. Eozoic, Cambrian, Devonian, Triassic, Cretaceous, Tertiary, Volcanics, etc. The carefully drawn map shows good geographical detail as well as remarkable geological information conveyed in strongly applied color. The geography of the map is from the War Department's "Military Map of the United States," used by permission of the Chief of Engineers.

References: Marcou & Marcou #70; Phillips (A) #1330.

Condition: B+

A colorful example with two edge tears at bottom that extend 1.25" into the image that have been repaired on verso with archival materials. There are a few additional edge tears and chips confined to the blank margins, and some faint dampstaining primarily in the bottom blank margin.