The 'Progress Maps' are amongst the most interesting, informative and useful maps of the Western land area. They show the routes of most of the earlier explorations and surveys, giving name and dates. Military posts, telegraph lines and railroads are shown. The solid color reflect survey maps published (gray) and under preparations (green). Clarence King's area of surveying responsibility (40th parallel) is also noted on this map. The legend helps locate completed Astronomical stations, military posts, telegraphs, and the expedition routes of the survey and exploration groups.

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Condition: A

Great coloring and strong, dark impression. Folding, as issued. Barely visible toning along a few folds.