Third System of Coastal Forts

“By these fortifications, supported by our navy, to which they would afford like support, we should present to other powers an armed front from the St. Croix to the Sabine, which would protect, in the event of war, our whole coast and interior from invasion ; and even in the wars of other powers, in which we were neutral, they would be found eminently useful, as, by keeping their public ships at a distance from our cities, peace and order in them would be preserved, and the government be protected from insult.”

—President James Monroe, Second Inaugural Address, March 4, 1821

How should a country protect its borders? The United States had to consider this question when the War of 1812 ended in 1815. One year later, the federal government believed it had an answer. The nation created a broad national defense strategy that included a new generation of waterfront defenses called the Third System of Coastal Fortifications.

The Board of Engineers for Fortifications, a committee of officers, met in 1816 to make a plan for national defense. They recommended the government maintain a strong navy, a standing army and reserve militia, a system of paved roads and canals to move troops and supplies, and a network of coastal forts. Each of these pieces relied upon the other to protect the nation from future foreign invasions.

Unlike First and Second system forts built between 1794–1812, Third System forts had durable construction materials and uniformity. Brick and stone forts were more resilient to time, nature, and battles. Masonry materials also allowed engineers to include essential features into their plans. Two important features included bombproof rooms, called casemates, and cannon openings, or embrasures. Casemates also provided stability, allowing engineers to build forts up to four stories. Sailing ships were no match for these titans of masonry capable of mounting 100 or more cannon.

The board focused its attention on creating new, and modernizing older, coastal defenses. It identified sites to fortify, chose design features, reviewed specific site selections, and evaluated feedback from project engineers. When the time came to begin construction, both free and enslaved tradesmen and laborers were used.
General Simon Bernard, a French officer and fort expert hired by the federal government, led the board. General Joseph G. Totten, a West Point graduate from Connecticut, later replaced Bernard. As the leading designers of the forts, no other individuals, military or civilian, influenced the Third System more than these two officers.

The board ultimately built 42 new forts along the Atlantic, Gulf, and Pacific coastlines. Though it stretched over many miles, the Third System worked together to protect the US. When completed, the fortifications were not immediately filled with soldiers and weapons, yet they gave the appearance of the nation’s military might.
Fear of standing armies, dating back to the American Revolution, shaped the public’s thinking on fort construction. First Lieutenant Henry W. Halleck, an Army engineer, defended the fort program in 1846. "When once constructed they require but very little expenditure for their support," he wrote. "In time of peace they withdraw no valuable citizens from the useful occupations of life. Of themselves they can never exert an influence corrupting to public morals, or dangerous to public liberty ; but as the means of preserving peace, and as obstacles to an invader, their influence and power are immense."
The Third System came to an end around 1867. More powerful weapons technology, like steel breech-loading rifled cannon and steel steam-powered warships, made the forts obsolete.

The 42 coastal forts were uniquely American. No other country had developed a coastal fortifications program like the Third System. The program was a massive undertaking, but one believed to be necessary to national defense. These forts reflect a bygone era, one in which American ingenuity protected the hopes and dreams of a nation through the strength of brick and stone.
A SHORT HISTORY.” Coast Defense Study Group. Accessed April 2, 2019.

Halleck, Henry W. Elements of Military Art and Science: Or, Course of Instruction in Strategy, Fortification, Tactics of Battles, &c.; Embracing the Duties of Staff, Infantry, Cavalry, Artillery, and Engineers. New York: D. Appleton & Company, 1846. Accessed April 2, 2019.

Herman, Marguerita Z. Ramparts: Fortification from the Renaissance to West Point. Garden City Park, NY: Avery Publishing Group, Inc., 1992.

Kaufmann, J. E. and H. W. Kaufmann. Fortress America: The Forts That Defended America, 1600 to the Present. Cambridge, MA: Da Capo Press, 2004.

Lewis, Emanuel R. Seacoast Fortifications of the United States: An Introductory History. 7th ed. Annapolis, MD: Naval Institute Press, 1993.

The Addresses and Messages of the Presidents of the United States, Inaugural, Annual, and Special, from 1789 to 1846: With a Memoir of Each of the Presidents, and a History of their Administrations; Also the Constitution of the United States, and a Selection of Important Documents and Statistical Information. Vol. 1. New York: Edward Walker, 1846. Accessed December 19, 2019.

Weaver II, John R. A Legacy in Brick and Stone: American Coastal Defense Forts of the Third System, 1816–1867. 2nd ed. McLean, VA: Redoubt Press, 2018.

U.S. Congress. House. A Bill authorizing the appointment of a Board of Fortifications, to provide for the sea-coast and other defences of the United States, and for other purposes of 1862. HR 416. 37th Cong., 2nd sess. Report Number 86. Accessed April 2, 2019.

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Last updated: April 17, 2020