From the 1880s to the 1950s, the U. S. Geological Survey used engraved copper plates in the process of printing many thousands of topographic and geographic quadrangle maps at several map scales.
Usually made from a copper alloy (a few from zinc), the heavy engraving plates were inscribed with the points, contour lines, symbols, and text that constitute a topographic map. The plates ranged in size from 4-by-5 inches to 36-by-40 inches; the majority measured 17-by-21 inches with an average weight of around 12.5 pounds each.
The Printing Process – From Plates to Paper
A complicating aspect of this historical USGS printing process is that prints were not directly made from the plates. USGS transferred the image from the engraved plate to a special lithographic stone in order to make large numbers of prints, an approach that preserved the crispness of the engraving. Otherwise, the accuracy of the engraving would have been lost due to the repeated pressure required to transfer the image directly from the plate to each paper copy.
For printing purposes, the copper engravings were mirror images (left-to-right reversed). Etched by a USGS cartographic technician called a “map engraver,” the words and text characters are backwards. For maps, “east” appears on the left side of the plate instead of the right as it does on the printed map.
The engraving plates for a topographic map were color-separated in a set; that is, there was a plate for each color of ink to be printed. A typical topographic quadrangle map had a set of three plates: a black ink plate for cultural features, boundaries, and most of the text; a blue inked plate for hydrography; and a brown ink plate for topographic contours. For a geologic quadrangle map of the same place, a fourth (and sometimes more) plate(s) in the set could be engraved with geologic features and printed in the desired color(s).
Similarly, engraving plates were used to print the scientific illustrations that were included in hundreds of USGS bulletins, professional papers, and geologic folios. A single-color illustration required one plate while a multicolor illustration was created by overprinting the engraved images of several plates using the appropriate color of ink.
Advances in Printing Technology
As more modern map compilation and printing methods made the engraving of plates obsolete, USGS started phasing out the engraving of plates in the 1940s, although some work lingered into the early 1950s.
Currently, the USGS still holds more than 13,400 engravings. The oldest are more than 125 years old; the most recent are around 60 years old. Physically, the collection has an estimated cumulative weight of 89 tons,
A Legacy to Share With the American People
As the originating agency, the USGS was, by default, initially in charge of the storage and disposition of the engraved artifacts. Since many experts in government and private mapping communities believe the engravings to have an inherent historical, artistic, and sentimental value, appropriate officials have sought to steer the clearance method in the direction of maximizing the likelihood of their preservation. Working in coordination with the General Services Administration (GSA) federal property disposal process, the USGS has been authorized to develop an atypical but logical process.
Initially, engravings were offered for donation to federal organizations, state and local governments, other public agencies, as well as educational nonprofit organizations such as universities and colleges, libraries, and museums. Following that part of the process, the remaining sets that were not requested for donation are subsequently being offered for sale to the public.
The GSA will sell the plates in “as is” condition. Most are tarnished and some are warped, pitted, scratched, or otherwise damaged from years of use and storage.
If you want to own a truly unique artifact of mapping history, go to the GSA auction site to join the bidding. The bidding for the current sets closes on April 1. Due to the volume of sets in storage, a second round of the donation process and sale is scheduled in the next few months.
View the GSA Auction site
For further details of the donation process: firstname.lastname@example.org