Begin DRTO Cannon Conservation Project

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Date: February 16, 2007
Contact: Linda Friar, 305-242-7714
Contact: Nancy Russell

16Dry Tortugas, FL:  The National Park Service (NPS) will begin a multi-year project to conserve the ten original cannon at Fort Jefferson in Dry Tortugas National Park. The six 15-inch Rodman smoothbore cannon and four 10-inch Parrott rifled cannon are some of the rarest and most significant examples of 19th Century seacoast artillery in existence.

In April 2004 the South Florida National Parks Trust funded a condition survey for the cannon. This work was completed by NPS metals conservator Gretchen Voeks and examined the existing condition of the cannon, as well as treatment options. Given the isolation of the Dry Tortugas and the size, weight and location of the cannon on the terreplein (or roof structure) at Fort Jefferson, it was decided that sensitive sandblasting corrosion from the cannon, followed by the application of a primer and paint system to seal out moisture, was the most reasonable approach to long-term preservation of these massive cannon.

The South Florida National Parks Trust continues to support this project and provided funding for conservation treatment of the first cannon, which will be completed February 22, 2007. Additional funding was received from entrance fees paid by park visitors, through the NPS Recreational Fee Demonstration Program. To date, funding is available to treat three of the ten cannon.

The NPS has contracted with Tuckerbrook Conservation of Lincolnville, ME to complete the treatment of the cannon. Conservators Ron Harvey and Jonathan Taggart will conduct the conservation. In addition to the challenges of isolation and logistics at Fort Jefferson, this project is particularly challenging because of the size and weight of the cannon. Each Rodman weighs approximately 25 tons, while each Parrott weighs approximately 15 tons.

The original ordinance at Fort Jefferson included dozens of flank-defense Howitzers, 90 10-inch Rodman smoothbore cannon, 60 10-inch Columbiads and various 8-inch Columbiads. In the early 1870s, an intensive modernization effort was undertaken. In 1872, the 6 Rodman cannon were installed on the terreplein at Fort Jefferson.

Fort Jefferson was never completed as originally designed. The fort’s garrison departed in 1874, and construction halted in 1875. It was subsequently occupied and put to various uses in the late 19th and early 20th Centuries, until the establishment of Fort Jefferson National Monument in 1935. By 1907, the original ordnance (except the 10 remaining Rodmans and Parrotts) had been removed. This original ordnance was sold to scrap dealers, or donated to towns and cities across the country for war memorials. Research has shown that most of the original flank-defense Howitzers from Fort Jefferson were later donated by these communities to World War II scrap metal drives. The loss of original ordnance from coastal forts is a common phenomenon; many forts have no surviving original ordnance and those that do generally only have examples of the smaller guns. The sheer size and weight of the 15-inch Rodman and 10-inch Parrott cannon at Fort Jefferson saved them from being taken off site or melted down for other purposes. These cannon are the only original weaponry on site to interpret to the 90,000+ annual visitors to Dry Tortugas National Park.

The Rodman cannon was invented by Thomas Jackson Rodman, an Army ordnance officer who graduated from West Point in 1837. Rodman’s process involved casting the gun barrel around a hollow core and cooling the metal from the inside. The result was a firm, tight casting without dangerous air fissures or cracks. Rodman applied for a patent in 1847; the U.S. Army subsequently adopted his process. The massive 15-inch Rodman cannon represent the apex of this smoothbore cannon technology. These cannon fired a solid shot, weighing 432 lbs., to a maximum range of three miles. The Rodman cannon at Fort Jefferson were cast in 1871, making them some of the last Rodmans to be produced. The six Rodmans at Fort Jefferson is the largest collection in existence and includes the only known example with an extant sight.

Although Rodman's process revolutionized coastal armaments, these cannon lost favor as the superiority of rifled barrels became evident against older forts. Even as Rodman perfected his process, rifled artillery was being cast that made these smoothbore cannon obsolete. Robert Parker Parrott, superintendent of the West Point Foundry, developed a rifled cannon that fired a pointed projectile, which could travel further and with greater accuracy, easily penetrating walls and making coastal forts indefensible. The 10-inch Parrott rifled cannon, which helped to revolutionize warfare, was the largest and rarest of these successful rifled cannon. They fired pointed, elongated projectiles, commonly weighing 250-275 lbs., to a maximum range of almost 5 miles. Only 42 10-inch Parrotts were ever manufactured; the collection at Fort Jefferson contains four of the 13 known surviving examples.

The cannon conservation project is the first phase of a project that will improve both the preservation of the cannon and the interpretation of the nationally significant Fort Jefferson. Ultimately the National Park Service plans to historically mount one of each type of cannon in reproduction carriages as funding allows, enabling the public to better understand the fort’s defensive system and its role in protecting US national interests in the 19th century.

Further information about Dry Tortugas National Park is available at Individuals seeking more information about the South Florida National Parks Trust, and its support of activities on behalf of Biscayne, Dry Tortugas, and Everglades National Parks, may call (305) 665-4769 or visit


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