coast defense

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Reference Sources Used for This Website

The most basic sources used here are reports by the U.S. Army on the harbor defenses of each harbor, for example the "Supplement to the Harbor Defense Project: Harbor Defense of Boston, Revised as of 31 January 1945." This is referred to as "HDBoston." This report contains a listing of all harbor defense Locations and sites, fire control buildings (including their coordinates and the batteries with which they were linked), gun batteries, radars, searchlights, submarine defenses, and command and control points, with an overview of the communications links between these elements. The report also describes the unit organization of the harbor defenses and has sketch maps of all Locations and sites that roughly positions their assets.

This report and many others of interest have been made available on CD/DVD by the Coast Defense Study Group (CDSG), who accessed the National Archives, scanned the original materials, and offered the results to the public for modest prices.

Another basic source are the Reports of Completed Works (RCWs) by the Army Corps of Engineers. These reports were issued when an asset (e.g., an emplacement for a gun battery, a fire control tower, or a latrine) had its construction completed or updated, and these have been collected and scanned for each harbor by the CDSG. Depending on the asset, these reports can include architectural plan and section drawings, checklists of performance criteria (e.g., types of fire control instruments and their heights above sea level), and details of armaments (gun types and models, gun carriages, fields of fire, etc.). Sometimes there are holes in these records (e.g., a known certain gun battery may not be included, or types of guns are not thoroughly described). The RCWs for Boston cover a range of dates from 1896 to 1946.

More general information about coast defense is provided by a marvelous compendium published by CDSG and entitled "American Seacoast Defenses: A Reference Guide," edited by Mark A. Berhow, 2nd Edition, CDSG Press, 2004 (623 pp.). This report (referred to here as "ASD") contains things like an article on the design and operation of shell hoists for the guns, a listing of all map symbols used for the Coast Artillery, pictures and data on a very large number of different guns, or a description of the different plotting boards in use by the fire control system.

CDSG has also retrieved and scanned the various series of maps published by the Army for the various harbor defense systems, These sketch maps tend to cover the periods of the 1910s, 1920s, 1930s, and 1940s seriatim, but these collections are not complete for each installation in all years, and gaps exist by harbor and year. The maps also vary widely regarding the accuracy with which they locate various emplacements (e.g., searchlight positions can be hundreds of feet off). Many of these maps have been reproduced here, and they are generally dated on their face.

A useful source for Boston is Butler, Gerald, "The Military History of Boston's Harbor Islands," Arcadia Publishing, 2000, which contains period photos of the various Boston forts.

An Excel spreadsheet-based formula for converting between the X-Y coordinates of the Boston harbor defense local grid system and latitude/longitude for these points has been developed by Jerry Wahl, a professional surveyor, and has been found to provide approximately 6-inch accuracy across the Boston harbor defense area. This conversion tool is available from

Coast Defense Study Group

The CDSG is an essential reference source for anyone with a serious interest in coast defense research.