A Brief History of American Seacoast Fortifications, 1830 - 1945

A Brief History of American Seacoast Fortifications, 1830-1945

Researched and Written by
Robert E. Duchesneau III

Early 1800's




The Statue of Liberty is built on top of a Second System fort.

In the early 19th Century the United States had constructed over 20 seacoast forts known as the Second System (the First System being forts "inherited" from the British, plus a few forts built in the late 1700's), but they were inadequate in both quantity and quality. The events of the War of 1812 had exposed the vulnerabilities of the Second System, especially since Washington, DC was captured and the Capitol burned, so Congress decided to build a comprehensive system of forts to protect each significant port in the country.


Fort McHenry, a First System fort with 1870's external batteries.

Although Fort McHenry in Baltimore, Maryland famously withstood the bombardment that inspired "The Star-Spangled Banner", other forts did not fare as well. In the 1830's, construction commenced on the Third System. The latest masonry fortification concepts were employed. French General Simon de Bernard assisted in designing the larger forts, such as Fort Monroe near Norfolk, Virginia and Fort Adams in Newport, Rhode Island. The principal American fortress engineer was Colonel Joseph Totten. His main innovation was the Totten casemate.


A 10-inch Rodman gun in a Totten casemate, Fort Knox, Prospect, Maine.


A 32-pdr seacoast howitzer in a Totten casemate, Fort Monroe, Hampton, Virginia.

In this design, the cannon pivoted about the narrowest part of the embrasure, allowing both a smaller embrasure and a wider field of fire than previous designs.


Fort Adams, Newport, RI. Second only to Fort Monroe in size. Note the "tenaille" on the right, a landward defense system in place of a moat.


A medieval-looking redoubt near Fort Adams.

The new forts were substantially complete by the 1850's, including modernization of older forts. The number of ports protected was far greater than in the Second System, with even the remote Dry Tortugas off Key West, Florida receiving the huge Fort Jefferson. The individual forts were better designed and equipped than previously.


32-pdr seacoast howitzers at Ft. Moultrie, Charleston, SC, in the typical upper tier mounting of a Third System fort.


Typical flank howitzer mounting, Ft. Pulaski, Savannah, Georgia.

Armament ranged from short 24-pdr (5.8 inch/147mm) flank howitzers for defense against land attack, to 10-inch (254mm) "Columbiads" (a smoothbore cannon of medium barrel length). The most common weapon was the 32-pdr (6.4 inch/163mm) seacoast howitzer.

Civil War




Bombardment of Fort Sumter.

The Third System forts played a significant part in the American Civil War (1861-65), starting with the bombardment and capture of Fort Sumter by the Confederacy in Charleston, South Carolina in April, 1861. Possession of the masonry forts proved crucial to keeping their associated ports open or closed. For example, by possessing Fort Sumter and other works, the Confederacy was able to keep Charleston open to blockade runners almost throughout the war, despite a Union Navy sea blockade and Union Army occupation of coastal areas at the harbor mouth.


Fort Monroe, Virginia.

The Union's occupation of Fort Monroe allowed the Peninsular Campaign to take place, which temporarily advanced to within a few miles of the Confederate capital of Richmond, Virginia. Besides the pre-war masonry forts, numerous earthen forts mounting heavy weapons were constructed at strategic points during the war.


15-inch Rodman gun at Fort Knox, Prospect (near Bucksport), Maine.


8-inch (foreground) and 10-inch Parrott rifles at Ft. Moultrie, Charleston, SC. An Endicott period battery is behind them.

The Civil War saw the development of two families of new weapons which would remain in service until 1905. These were the Rodman heavy smoothbore cannon and the Parrott heavy rifled cannon. Both types were muzzle-loading. The Rodman guns were manufactured by an improved process that allowed a heavier powder charge and a larger caliber than the previous Columbiads. The most-used calibers were 10-inch (254mm) and 15-inch (380mm). Parrott rifles were made in calibers ranging from 10-pdr (3-inch, 76mm) to 300-pdr (10-inch). The 300-pdr, 200-pdr (8-inch, 203mm), and 100-pdr (6.4-inch, 163mm) were used as heavy fortification weapons.

Late 1800's

After the Civil War, most of the Third System forts were re-armed with the new weapons, and new earthen batteries were constructed in some locations. Re-armament usually meant construction of earthen batteries just outside the forts, as the 15-inch Rodman was too large for use in the older casemates. A fort would now typically have mountings for 5-6 15-inch Rodmans and 8-10 10-inch Rodmans and/or 8-inch "converted" rifles. These last were made by lining down a 10-inch Rodman with a rifled sleeve. The masonry forts retained their flank howitzers and their role in defense against land attack. Usually, a portion of the casemates would be occupied by 10-inch Rodmans.


20-inch Rodman gun, near Fort Hamilton, Brooklyn, New York.

In the 1870's, three 20-inch (508mm) Rodman guns (originally intended for the never-completed super-Monitor "Puritan") were placed in New York harbor forts. Two of these weapons still exist, one in Brooklyn, New York and the other at Sandy Hook, New Jersey.

Endicott Period

The development of high-velocity rifled guns eventually made the Third System obsolete. In 1885, the Endicott Board recommended a comprehensive upgrading of harbor defenses nationwide. Several new weapon systems were rapidly developed. One was a controlled minefield system for harbor approaches. The mines were command detonated from observation towers on shore. The advantage of command detonation was that no gaps were required for passage of friendly shipping. Another weapon was the 12-inch (305mm) armor-piercing, breech-loading mortar. These were emplaced in groups of 8 or 16 in positions concealed against observation from the sea.


12-inch mortar pit with 4 mortars.



14-inch disappearing gun at Ft. MacArthur, Los Angeles, California.

Finally, the disappearing breech-loading rifle was developed. This weapon was normally concealed below the edge of a parapet designed to look like a hill or ridge from the sea. The weapon was counterweighted to be raised just before firing, then sink down for reloading.


14-inch disappearing gun being reloaded.

Disappearing guns ranged from 6-inch (152mm) to 12-inch (305mm). Later, 14-inch (356mm) weapons and a single 16-inch (406mm) disappearing gun were developed. The 10-inch (254mm) gun was the most frequently used. 3-inch (76mm guns) were also emplaced for "mine defense", to drive off enemy minesweepers. A typical harbor approach was protected by 8-10 heavy (>6") and about 6 light guns, plus 8-16 mortars.


10-inch disappearing gun firing.

The Endicott system provided comprehensive, concealed protection against attack from the sea. The numerous observation towers were camouflaged as beach cottages, lighthouses, or even church towers. All emplacements were sited to provide maximum coverage of harbor approaches. In most locations this meant building new emplacements, but some Endicott batteries were built right into Third System forts, such as Fort Delaware and Fort Sumter. Much of the system was complete by 1898, with construction continuing past 1910. It was the most comprehensive American coast defense system yet built. As the Endicott system was completed, the 40-year-old Rodman guns were retired from harbor defense. Some of them were simply left in place, where they can be seen today, as at Fort McHenry.

After a few years, it was noticed that the tight arrangement of four mortars per pit made it difficult to rapidly reload the weapons. So, two weapons were removed from each pit, which nearly doubled the rate of fire. The removed weapons were not re-emplaced, with most eventually being rail mounted in World War I.

The Endicott system's only major weakness was a complete lack of defense against attack from the land. Endicott batteries were also unprotected against air attack, although the airplane was developed after the Endicott system was complete. These weaknesses proved significant in the failure of Endicott batteries to prevent severe losses in the only campaign in which they were involved, the defense of Bataan and Corregidor in the Philippines in 1942.

Taft Period

The next major upgrade of American coast defenses occurred in the 1920's. A number of improved 12-inch (305mm) guns had become available, and the cancellation of several battleships under the Washington Naval treaty had made numerous 16-inch (406mm) guns available. Although the airplane was recognized as a threat, the new emplacements only partially protected against it. Magazines were in heavy concrete-and-earth bunkers, but weapons were on open concrete platforms known as "Panama mounts" (a number of them being in the Panama Canal Zone).


16-inch gun on Panama mount.


14-inch railway gun.


8-inch railway gun at the University of Tampa, Florida. This weapon is mis-identified as a disappearing gun that was formerly on the site from Fort Dade, Egmont Key.

Railway artillery was added in a few locations, principally in Panama and Los Angeles, California. The railway guns were 8-inch (203mm) and 14-inch (356mm), with some 12-inch mortars. Several hundred of the smaller-caliber weapons had been produced for World War 1, but few or none of them saw action.


16-inch gun in casemate (top), 6" shield gun (bottom).

The late 1930's saw the ultimate development of American coast defense. All-new casemates for pairs of 16-inch (406mm) guns were constructed at every significant port. These new emplacements were fully protected against air attack with a thick concrete overhang above the gun and a shield on the gun mounting. They resembled the later German "Atlantic Wall" large gun emplacements. In some cases, existing open 16-inch or 12-inch mountings were roofed over in the same manner. Another heavy coast defense mounting of World War II was of two triple 14-inch turrets from the sunken "Arizona" in Hawaii. The 16-inch mountings were accompanied by pairs of 6-inch (152mm) guns in single open-back turrets with a concrete magazine between them. Unlike the Atlantic Wall, no infantry bunkers were constructed. Construction on the 16-inch system continued through the early part of World War II. As this system was completed, the disappearing and other previous guns were scrapped to support the war effort. The scrapping of these weapons was almost complete. Only a few weapons in the Philippines and on some islands survive today. The surviving weapons in the US are at Ft. Casey on Whidbey Island in Washington state, Ft. DeSoto in St. Petersburg, Florida, and Ft. Pickens in Pensacola, Florida. Plus a single 6" gun at Sandy Hook, New Jersey, and two 3" and a 90mm at Ft. Monroe.

World War Two

World War II saw the only employment of an American coast defense system in combat since 1865 (except for a 6" battery in Oregon that was fired on by a Japanese submarine in 1942). The story of the defense of the Philippines in 1941-2 is on the Web at this location. Basically, few of the weapons were capable of bearing against the Japanese attack from the land (many were on small islands far from the action), and even fewer were protected against air attack. However, the Malinta Tunnel on Corregidor, constructed as the harbor defense headquarters, proved crucial in enabling the defenders to hold out until May, 1942. If a Maginot-style land defense fort system had been built in the 1930's to support General MacArthur's defense plan for the Bataan peninsula, perhaps the outcome of the Japanese invasion of the Philippines would have been different. However, except for the mostly wooden stockades constructed against Indian attacks, land defense forts had not been built by the United States since 1865, and seem to have passed from American military thinking at the same time.


Nike anti-aircraft missiles. Nike-Hercules (left), Nike-Ajax (right).

With the end of World War II, the American coast defense system was no longer needed. Most of the coast artillery units had converted to air defense units. The remaining emplacements were abandoned and the weapons scrapped. In the early 1950's, the Nike missile system was constructed to protect the periphery of the United States against air attack. The Nike system used previous coast defense sites at numerous locations. This system was dismantled in the early 1970's, ending an era of fixed defenses that began at the birth of the nation.

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