USA, Grand Canyon of the Colorado, Routes of Exploration Parties, 1871.

"Map Showing Routes of the River and Land Parties Engaged in Exploring the Grand Canyon of the Colorado ... 1871" drawn by Weyss, Thompson and Lang after P.W.Hamel and L.Nell, issued Feb 4th 1878 under the direction of Brig. Gen. A.A.Humphreys. Tinter lithographic map. Several folds as published, slight foxing and closed tear of about 5 cms into left side (no loss.) Size 41 x 41 cms plus good margins. Ref F182