
The U.S. Army's Coast Artillery Corps was charged with the task of defending United States against naval attack and manned the fixed defenses located around the major deep-draft harbors.
The modern-era harbor defenses consisted of several reservations of land on which were located the fortifications and support structures designed to keep enemy ships from entering the harbor:
This website provides information on the various elements that made up a harbor defense illustrated with examples from the harbor defenses of the Pacific coast. The forts of the Pacific coast are excellent places to view the coast artillery past. Most of the fortification structures remain at these locations today, and most are are now parks and open to the public. These defenses have been extensively documented on the web by the CDSG and several other organizations.

A brief history of American seacoast defense

Underwater Defenses (Mines)

Garrison buildings

Coast Artillery Units
Photo gallery of remaining American seacoast artillery weapons
Modern Era Harbor Defense Locations (1890-1945)
US North Atlantic Coast (online html fort & battery list)
US Mid Atlantic Coast (online html fort & battery list)
US South Atlantic Coast (online html fort & battery list)
US Gulf Coast (online html fort & battery list)
US Pacific Coast (online html fort & battery list)

Harbor Defenses of Puget Sound, Washington

Harbor Defenses of the Columbia River, Washington and Oregon

Harbor Defenses of San Francisco, California

Harbor Defenses of Los Angeles, California

Harbor Defenses of San Diego, California
Hawaii (online html fort & battery list):
Manila & Subic Bay, the Philippines (online html fort & battery list):
Panama Canal Zone (online html fort & battery list ):
Other Atlantic & Caribbean defenses (online html fort & battery list)
For more specific information on the other US harbor defenses visit these Websites:
FortWiki: US Harbor Defenses
The links catalog page to a detailed website with information and photos on nearly all US forts and batteries
For more information on documentation see the page on Key Documents and References.
Examples of harbor defense documentation can be downloaded as PDF files from the Harbor Defenses of the Columbia webpage.
Order documentation PDFs on the American seacoast defenses from the CDSG ePress
Much more detail can be found in the CDSG publication American Seacoast Defenses: a Reference Guide