Fort Delaware State Park, Delaware City, DE
It has been a basic military policy of most nations to secure their borders against possible attack through the construction of defensive fortifications. Except for an attack from Canada or Mexico, all American adversaries would have to come from overseas. The United States sought security against an attack through fortification of her maritime frontiers. Fortifications were viewed both by the U.S. Congress and the American public as a way to avoid foreign entanglements and war. This thinking had a strong influence on American national defense policy and during certain periods fortification construction was nearly a substitute for any other form of military policy.
Seacoast fortification was attractive to the United States government. Few military principles were as enduring as that of the superiority of guns ashore over those afloat. The United States had a long shoreline, a weak navy (at least until the early 20th Century), and a concern about foreign attack. The use of seacoast fortifications also complied with another long standing American military tradition--militia forces. Seacoast fortifications, once constructed, could be maintained by a caretaker force.
Golden Gate National Recreation Area, San Francisco, CA
The American government invested large sums of money in several major peacetime coastal defense construction programs: the "First System" (1794-1800), the "Second System" (1804-1812), the "Third System" (1816-1867), construction after the Civil War (1870-1875) the "early modern programs" (Also known as the "Endicott Board", "Taft Board", and "post-WWI" programs) (1890-1930s), and the Harbor Defense Modernization Programs of the 1940s (1940-1945). Manning the coastal defenses was a major mission of the U. S. Army for over 150 years. After 1907, the Army had a professional service that was specifically dedicated to operate these complicated weapons: the Coast Artillery Corps (C.A.C.).
Fort Columbia State Park, Chinook, WA
Advances in weaponry after 1940 made the coastal artillery nearly obsolete by the end of World War II. The airplane became the ascendant military weapon, which resulted in the conversion of coast artillery units into antiaircraft artillery units. By 1950 the US Army had dismantled all its fixed gun harbor defenses.
First, Second & Third Systems
Civil War & Post-Civil War periods
Early Modern Programs (Endicott & Taft)
US Coast Defense Sites 1945-2004