Map of the Month--November 2014

Map showing the position of the main ground-water table on Long Island, New York, 1904. Brooklyn Historical Society Map Collection.

For the November Map of the Month, I have chosen a relative newcomer to the catalog, “Map showing the position of the main ground-water table on Long Island, New York,” published by the U.S. Geological Survey in 1904. This map landed on my desk with 2 others, “Map of Long Island, New York showing location of wells” and “Map showing the waterworks systems of Long Island, New York.” All bore plate numbers from “Professional Paper No. 44.” A quick catalog check found this paper to be Underground Water Resources of Long Island, New York, weighing in at 385 pages with both a general index and an index of well data. The report is, as one would expect, quite detailed, and with 34 plates and 71 illustrations and maps, thoroughly documented. This map, at 16 x 31”, is by far the smallest of the three extracted for individual cataloging.

The City of Brooklyn had been increasingly dependent on the water resources of western Long Island throughout the 19th century. As the population grew, the Brooklyn system for water supply extended as far east as Massapequa to pump water to the Ridgewood Reservoir. These wells can be seen in the solid blue dots on the detail below:

Map showing the position of the main ground-water table on Long Island, New York, 1904, detail. Brooklyn Historical Society Map Collection.

Other easily identified details on this map are the wells from perched water tables shown in red. (Perched water sits above the water table atop an impermeable layer.) The blue shading indicates areas of artesian flow, where water from the water table flows to the surface under its own pressure. The broad contour of Long Island’s geologic makeup can be easily seen in this contrast between the red-dotted north and the blue-shaded south. The map also shows contour lines indicating the depth of the water table over the entire island.

According to the Encyclopedia of New York, one reason Brooklyn consolidated with New York in 1895 was to gain access to the New York water supply and the Croton Reservoir system. The New York City Department of Water Supply was created in 1905, and after study, it chose the Catskill region for development of the New York City water supply. No doubt this map, and the report from which it came, helped inform that decision.

Interested in seeing more maps? You can view the BHS map collection anytime during the library’s open hours, Wed.-Sat., from 1-5 p.m. No appointment is necessary to view most maps.

This map was cataloged with funding provided by a Council on Library and Information Resources (CLIR) “Hidden Collections” grant.