Darton, N. H. [MAP] Hypsometric Map of a Portion of South Dakota and North Dakota (1896). New York: Julius Bien & Co., 1896. 
11 1/4 x 14 1/2 inches, a beautiful and unusual color map showing topographic lines and the water resources of this region, suitable for framing. Very good.
"Also showing by numbers in blue the feet above sea-level to which the artesian waters will rise, as calculated from the pressures in the wells."
Extracted from the Seventeenth Annual Report, U. S. Geological Survey.