The Fortified Islands: Naos, Culebra, Perico, and Flamenco
Linked by a 2.5-mile causeway, initially built as a breakwater to stabilize turbulent waters near the canal, this structure eventually included a critical railway for moving troops, artillery, and supplies swiftly across the defensive network. A striking aerial photograph (below) from 1932 highlights the defensive ingenuit
y of the Fort Grant complex. These man-made islands bristled with artillery, creating an ironclad barrier protecting the Pacific entrance of the Panama Canal:
The 1932 aerial photograph shows the main base located in the extreme background with the four fortified islands of Fort Amador.
Flamenco Island (Foreground): Featured two Model 1910 (M1910) 14-inch rifles on disappearing carriages (DC M1907MI) emplacement's on the summit.In addition to the 14-inch rifles atop Flamenco Island, the Army constructed a series of three mortar batteries in six dual pits, each having four 12-inch M1912 mortars installed on M1896MIII carriages.
Perico Island: (The Second Island) Hosted one 16-inch rifle (M1895) mounted on a disappearing carriage (M1912), whose long-range firepower significantly exceeded even the railway guns.
Culebra Island: (Far Left, Third Island) The Army constructed firing turntables on piles for two dismounted 14-inch M1920 railway guns. Remarkably versatile, these powerful weapons could fire directly from railway mounts while the train was traveling from Atlantic coast Fort Randolph to Pacific coast Fort Grant, or be quickly dismounted and repositioned onto stationary platforms to increase their effectiveness and accuracy. The island also supported two 155mm guns on Panama mounts, as well as several 75mm guns on mobile mounts.
Naos Island (Last, Fourth Island): Armed with Batteries Buell and Burnside. Each of the two batteries mounted two 14-inch rifles (M1910) on disappearing carriages (DC M1907MI). This installation served as a lethal barrier, capable of inflicting devastating damage upon hostile fleets.
Strategic Importance of the Islands
The so-called “Fortified Islands”—Naos, Culebra, Perico, and Flamenco—stretch along the eastern side of the Panama Canal’s shipping channel. Their positioning, approximately 12,000 to 14,000 yards south of the Miraflores Locks, was deliberately chosen for their strategic advantage. From here, the U.S. military could effectively repel any hostile naval approach before enemy forces could threaten the canal’s essential installations.
Connecting these islands to the mainland was a vital reinforced causeway equipped with a rail line, instrumental in the construction, resupply, and manning of coast artillery batteries and underwater minefields. Later, the causeway seamlessly supplied ammunition, equipment, and artillery units, including mobile railway guns, ensuring swift and decisive responses to potential threats.
The fortified islands were all gradually turned over to the Republic of Panama from 1979 to 1999 by order of President Jimmy Carter, and the area is now failing as a major tourist attraction and leisure area. Today, President Donald Trump is making moves to restore the Panama Canal Zone to United States control.
Fort Amador/Fort Grant on the Pacific Side
(with Culebra Island railway gun dismount sites)
The United States Army deployed two 14-inch M1920 railway guns, a powerful weapon system, to the Panama Canal Zone, specifically for canal and harbor defense. The 14-inch railway guns first arrived in 1928, a rare example of enhancement of Canal defenses between the world wars. They had firing points at Fort Randolph at the Atlantic end of the Canal, and on Culebra Point at Fort Grant at the Pacific end. They were capable of either being dismounted to fire from fixed positions, or they could also be fired while mounted on its railcar platform while shifting between the two opposite coastal fort positions located about 47 miles apart on their respective coasts.
Guardians of the Panama Canal: The Mighty 14-Inch Railway Guns of Fort Grant During World War II
During the tense years between World War I and World War II, the Panama Canal—a vital lifeline for global trade and military mobility—was shielded by an engineering marvel: the colossal 14-inch M1920 railway guns. These mobile artillery titans arrived in 1928, marking a rare upgrade to the Canal’s defenses during an era of relative peace. Stationed at strategic firing points at Fort Randolph (Atlantic entrance) and Culebra Point at Fort Grant (Pacific entrance), these guns boasted a jaw-dropping range of 48,000 yards (27 miles)—double the reach of earlier 14-inch fixed emplacements. Imagine shells soaring over distances greater than the length of Manhattan Island, ready to repel any threat to this engineering wonder of the world.
Fort Amador and the Fortified Islands: A Network of Steel
From Mudflats to Military Might: The Story of Fort Amador
In August 1911, when the Army broke ground in preparation for the construction of the Pacific fortifications, the area now known as Fort Amador was little more than a broad stretch of mud flats and swamp. Used as a dump for material removed from the canal, the area was appropriately referred to as “Balboa Dumps.” The Isthmian Canal Commission, however, had started building a breakwater from the dump area to Naos Island to protect the canal channel from cross currents. This breakwater was later extended to connect Naos with the other three islands. The flats on both sides of a portion of the breakwater were filled in to create Fort Amador. The breakwater that now constitutes the causeway extending from Fort Amador to the islands was solidly ballasted to support a railroad bed. During the construction phase, the railroad was used to carry material and machinery to the islands; later it was employed in hauling ammunition for the big guns, and when two railway guns were placed in service, the rail line was used to bring the guns to their firing positions on Culebra Island.
The Army started constructing quarters, administration buildings, and other permanent structures in 1915 and completed them by 1917. Fort Amador initially had three field grade officers’ quarters, one stable and wagon shed, eight company-size barracks, four four-family quarters, six two-family quarters, five noncommissioned officers’ quarters, one commanding officer’s quarters, one headquarters building, water and sewer system, and paved roads. The reservation contained many long ridges and deep ravines due to soil dumped by railcars, so the Army had to invest in additional fill and extensive grading.
Creating Fort Amador
Although Fort Amador was built and used primarily for housing the Coast Artillery Corps units that manned the big guns of Fort Grant, some armament was installed. The Army began building Batteries Birney and Smith in 1913 on the southern extremity of the post, on a little rise just north of the causeway; each battery had two six-inch disappearing guns (M1908 guns with M1905MII carriages). They remained in service until 1943, when the guns were removed and the structures buried. The Army replaced them with a 90mm anti-motor torpedo boat (AMTB) battery; the Army disarmed and buried the AMTB battery in 1948.
The first Army unit to be assigned to Fort Amador was the 81st Company, Coast Artillery, on 31 December 1913, followed by other coast artillery companies as the harbor defenses were completed. These companies were later organized into the 4th Coast Artillery (Harbor Defense) Regiment. In 1926, the 65th Coast Artillery Regiment was added to man the canal’s new antiaircraft defenses. During World War II, the Army deployed additional units and formed the Pacific Coast Artillery Brigade. Fort Amador also served as the headquarters of the U.S. Army Coast Artillery District (1919-47). Its coast artillery role ended in 1947 when the batteries of Fort Grant had been retired and armament removed.
Fort Amador then served as the headquarters of the senior Army commander in Panama from 1947 through September 1979—from the Army Caribbean Command (1947-63) through U.S. Army, Southern Command (1963-74) to the 193d Infantry Brigade (Canal Zone). After the Army headquarters moved to Fort Clayton in September 1979, part of the Army’s sector of Fort Amador and the islands were transferred to Panama on 1 October 1979. Most of post became headquarters of the Panamanian Defense Force until 1989. During Operation JUST CAUSE, Fort Amador was secured by 1st Battalion, 508th Infantry (Airborne), through an air assault with several buildings receiving damage from direct fire from 105mm howitzers and M60 machine guns. Portions of the post remained under American control until it was completely transferred to Panama on 1 October 1996.
Flamenco Island: From Civil War Hero to Cold War Sentinel
Long before it became a fortress, Flamenco Island hosted an unexpected guest: Ulysses S. Grant. In 1852, decades before he led Union armies or became president, a young Lieutenant Grant camped here during the 4th Infantry’s grueling trek across Panama to California. Little did he know this mosquito-ridden islet would one day bear his name as part of the “Fortified Islands”—a chain of four strategic outposts guarding the Panama Canal.
The Iron Gauntlet of the Pacific
The four islands which comprised the “Fortified Islands” extend along the east side of the canal channel and were an ideal location for defensive fortifications. Being 12,000 to 14,000 yards south of Miraflores Locks, the islands were strategically placed to engage a hostile naval force before it could come within range of the Panama Canal’s vital installations. The causeway’s rail line linking these four islands with the mainland was used for constructing, supplying, and manning the coast artillery batteries and the controlled mine facilities.
Battery Warren: Flamenco’s Steel Crown
Battery Warren on Flamenco Island mounted two Model 1910 (M1910) 14-inch rifles on disappearing carriages (DC M1907MI). With a traverse of 170 degrees and a range of approximately 24,000 yards, the two 14-inch guns commanded the entire area of seaward approach except for a small dead space behind Taboga Island. Located on the summit of Flamenco Island, the most seaward of the group, the battery was named in honor of Major General Gouverneur K. Warren.
Work began on Battery Warren in early 1912 and was completed, with guns installed, by 1917. Battery Warren included space for ammunition storage, fire control and plotting rooms, and power and communications systems. During construction, a special heavy-lift elevator was installed in a vertical shaft which was sunk 200 feet from the summit to connect with a horizontal tunnel which was entered from the mortar batteries on the north side of the island.
Practice firings were conducted regularly, with No. 1 Gun firing a total of fifty-seven practice rounds and No. 2 Gun 187 rounds. They were last fired on 8 December 1944, after which both guns were placed on secondary manning status. The four 155mm GPF guns on Panama mounts located in front of the battery were withdrawn at the end of World War II. The 14-inch guns were dismounted and scrapped in 1948.
The battery site continued to be used by Battery D, 764th Antiaircraft Artillery Battalion, using mobile 120mm guns from 1950 to 1960. Battery Warren was converted for use as a site for the HAWK missile system in 1960 when Battery F, 67th Artillery, later redesignated Battery C, 4th Missile Battalion (HAWK), 517th Artillery, arrived at Fort Grant. Much of the battery’s underground area was used in connection with the operation of the missile battery, while the concrete gun emplacements were filled in to provide sites for the mobile missile launchers and radar sets.
The Mortar Trio: Merritt, Prince, and Carr
In addition to the 14-inch rifles atop Flamenco Island, the Army constructed a series of three mortar batteries in six dual pits on the landward side of the island just above the shoreline and designated them Batteries Merritt, Prince, and Carr. Battery Merritt was named for Major General Wesley Merritt, Battery Prince for Brigadier General Henry Prince, and Battery Carr for Major General Joseph Bradford Carr.
The three mortar batteries were similar, each having four 12-inch mortars. The mortars were M1912 that were installed on M1896MIII carriages located in high-walled concrete emplacements, which contained magazines, plotting rooms, and a large power plant. The mortars had a range of 17,900 yards and a 360-degree traverse, permitting them to cover all approaches to the canal. At extreme range, rounds could be dropped about one mile beyond Taboga Island. The Army began construction of the batteries in 1912 and all weapons were in place by 1916. All were scrapped in 1943.
The area formerly used to accommodate these three mortar batteries was the site of barracks, a mess hall, and administrative buildings for Army antiaircraft artillery, and later the HAWK missile unit until 1970. The Army used Flamenco Island as a storage area until 1979 when the island was transferred to Panama. Under General Manual Noriega, the island was used as a political prison until 1989. It was subsequently handed over to the Panamanian national maritime service; this later moved to the former Rodman U.S. Naval Station in 1999. Around 2002, a two-level shopping mall was built over two of the mortar batteries (except for Battery Merritt) and part of Battery Warren was destroyed for a hotel that was never built. The battery’s unique access tunnel and elevator shaft still exist but are abandoned.
Battery Newton on Perico Island, Fort Grant, featured a one-of-a kind 16-inch fixed disappearing gun that recoiled down into a pit when it was fired. It took the Army seven years to construct the gun itself and then ten more years trying to determine what to do with it, which eventually was to install it on a custom-designed disappearing carriage at Fort Grant.
A Name Divided: The Fort Grant vs. Fort Amador Controversy
Fort Amador, originally known as Fort Grant, was named to honor General Ulysses S. Grant—the renowned commander of Union forces during the American Civil War and later the 18th President of the United States. Interestingly, Grant himself spent several weeks stationed on Flamenco Island in 1852, as part of the 4th Infantry Regiment’s arduous journey to California via Panama.
Fort Grant or Fort Amador?
When the War Department officially named the site "Fort Amador" in 1911, the term failed to catch on immediately, with the area popularly continuing to be called "Fort Grant" for several years afterward. Initially, the Army's naming practices for fortifications along the Panama Canal were informal and loosely defined, leading to ambiguity and widespread use of both names.
There was a brief consideration to name one of the artillery batteries after Dr. Manuel Amador Guerrero, Panama's first President. However, Panamanians viewed such a limited tribute as insufficient recognition for their leader. In response, American authorities decided instead to name the mainland section of the reservation in President Amador’s honor. The islands would continue to be referred to as Fort Grant.
Yet, despite the official naming in 1911, it wasn’t until 1917—after a formal protest from President Amador’s widow about the Army's persistent use of "Fort Grant"—that the name "Fort Amador" was definitively mandated. The Commanding General of the Panama Canal Department officially decreed (Order No. 16, October 19, 1917) that the correct designation, "Fort Amador," should thereafter be used exclusively for both the mainland and the islands.
Still, to this day, the name "Fort Grant" lingers in American historical and cultural references.
One of the two 14-inch two railway guns on Culebra Island is shown dismounted here in a 1932 photograph. Notice the front and rear railroad bogies located just out from under the gun emplacement. Behind them an ammunition car to support the gun can be see on the right.
Culebra Island: From Artillery Giant to Nature’s Classroom
In 1928, Culebra Island became the Panama Canal’s ultimate artillery showroom with the arrival of two 14-inch M1920 railway guns. These mobile railroad monsters could hurl 1,400-pound shells 48,000 yards (27 miles)—double the range of older coastal batteries. This was double the range of the 14-inch rifles of Batteries Buell and Burnside. Imagine a projectile soaring farther than the length of Manhattan!
The Railroad Titans (1928–1948)
The first gun was placed on a temporary spur at Fort Amador to await the rebuilding of the causeway railroad track and the completion of two firing positions on Culebra Island. The following year the second gun arrived.
The Army constructed firing turntables on piles at both Fort Randolph on the Atlantic side of the canal and at Fort Grant on Pacific side, so these two railway guns could travel across the isthmus depending on the greatest enemy threat. The guns could also be fired from their railroad mounts, though when dismounted into fixed positions, the range and accuracy was greatly increased with a more powerful round fired.
Long garage-like magazines with overhead trolleys which were cut into the island adjoining the track were built near the two firing positions on Culebra Island. The island also supported two 155mm guns on Panama mounts, as well as several 75mm guns on mobile mounts.
The United States transferred Culebra Island to Panama on 1 October 1979 and it was largely abandoned except for a beach house built by General Noriega. Dictator Manuel Noriega claimed a beachfront villa here, turning the island into his private retreat.
In 1992, the island became the Punta Culebra Nature Center as a facility for science education and to foster connections between Panamanians and their natural heritage. The center is run by the Smithsonian Tropical Research Institute and turned the 14-inch railway gun ammunition storage into exhibit and conference space.
Naos Island: The Pacific’s Forgotten Artillery Sentinel
Perched atop a 100-foot volcanic ridge, Naos Island once bristled with some of the most formidable firepower in the Panama Canal Zone. Its twin artillery bastions—Batteries Buell and Burnside—stood as silent guardians against naval threats, Each of the two batteries mounted two 14-inch rifles (M1910) on disappearing carriages (DC M1907MI). With a range of some 24,000 yards and a 170-degree traverse, the large caliber guns covered virtually every possible approach to the Pacific entrance of the canal to unleash chaos on any enemy daring to approach the Canal’s Pacific entrance.
The Giants of Naos (1912–1948
Each battery was an independent installation with its own ammunition magazines, plotting rooms, and communications systems, with an underground passage that connected all four guns. Construction of the two batteries began in 1912 and was completed by December 1916. During regular practices, No. 1 Gun, Battery Buell, fired 119 rounds and No. 2 Gun fired 102 rounds. No. 1 Gun, Battery Burnside, fired a total of ninety-four practice rounds and No. 2 Gun shot 105 rounds.
By World War II, the four 14-inch rifles were considered obsolete, and although they were fired as late as 15 November 1943, they were not manned in 1944-45. The guns were dismounted and scrapped in late 1947 or early 1948. The emplacements for Batteries Buell and Burnside were used for storage of civil defense supplies and for the U.S. Army Forces, Southern Command, Museum until 1 October 1979, when Naos Island was transferred to Panama.
The Hidden Support Network
Naos Island was also the site of Battery Parke, named in honor of Major General John G. Parke. The battery was equipped with two 6-inch rifles (M1908 on M1905MII disappearing carriages), each with a range of 6,000 yards. The battery was constructed from 1913 to 1915 and its armament was removed and dumped at sea in August 1946. Located just east of Battery Burnside but at the island’s waterline, it was destroyed in 2004 to make room for a large residential condominium structure.
Located on the north side of Naos Island was a mine storehouse, cable tank house, explosive magazine, loading room, mine casemate, power plant, and mine boathouse and wharf to support the control mine defenses of the approaches to the Panama Canal. While the composition of this underwater defense varied from 1916 to 1950, by the end of World War II there was an outer defense of sixteen groups of thirteen M4 ground mines and an inner defense of ten groups of thirteen M4s. A fleet of Army mine planters, distribution box boats, and yawls were stationed at Naos Island. Three ordnance workshops were located on the island and used for storage and repair of the guns of Fort Grant. Behind these buildings were long staircases that ran up to Batteries Burnside and Buell for gun crew access.
Decline and Reinvention
The top of Naos Island and the 14-inch batteries were filled in to prepare for the construction of a hotel that was never built. The fire control stations for these batteries have been destroyed for the construction of a large water tank. The control mine complex is currently occupied by the Smithsonian Tropical Research Institute’s Marine Laboratories.
Perico Island: The Giant Gun That Guarded the Panama Canal
Perico Island, one of the Panama Canal’s “Fortified Islands,” once hosted one of the most colossal weapons ever built by the U.S. Army: Battery Newton. Named in honor of Civil War Major General John Newton, this engineering marvel was home to a 16-inch M1895 rifle—a behemoth so massive it took seven years to forge (1895–1902) and weighed as much as 70 pickup trucks (284,000 pounds). It was erected on top of Perico Island at an elevation of some 230 feet.
The Gun That Disappeared
The battery consisted of one 16-inch rifle (M1895) mounted on a disappearing carriage (M1912). This was the largest Army weapon of its type at the time and was one of two such weapons on disappearing carriages, the other being an M1919 gun on an M1917 carriage as part of the Long Island Sound defenses on Great Gull Island (Fort Michie). This 35-caliber gun had a range of 22,600 yards and a traverse of 170 degrees. The gun weighed 284,000 pounds and took seven years to complete (1895-1902). It was not until ten years later it was shipped to Panama. Its limited of elevation of only twenty degrees on the disappearing carriage resulted in its 2,400-pound shell traveling a relative short distance.
Construction of the emplacement for Battery Newton began in 1914 and all work, including the mounting of the 16-inch rifle, was completed by 1917. To aid construction and ammunition deliveries, the Army constructed a rail line to the top of Perico that wrapped around the island. The Army also built a special concrete staircase to allow the gun crew to scramble from their seashore barracks up to the gun emplacement. In early 1943, the gun was placed on standby manning basis and was dismounted and scrapped later that same year.
The site of Battery Newton was converted for use as a radar installation originally operated by the Federal Aviation Agency (now by Panama’s Autoridad Aeronáutica Civil) for civil aviation in the region. The underground facilities are abandoned but the old railroad bed, including a tunnel near the top of the hill, still remains.
As the Army retired its coast artillery installations at Forts Amador and Grant, they were repurposed for other functions. Battery Newton and its 16-inch disappearing gun on Perico Island was replaced by a radar site first operated by the Federal Aviation Administration and later by the Panamanian Autoridad Aeronáutica Civil.
Map View of Pacific canal entrance at Fort Amador, showing the causeway to the four islands.
Close-up Map View of the four islands at the canal entrance at Fort Amador.
