In the centuries before the invention of the internal combustion engine, a large, navigable river was typically a major thoroughfare – but it could also be a major obstacle, and not just for crossing. Controlling river access could be key to hindering the movements of invaders. As the American Revolution got underway, the strategic importance of the Hudson – then still known as the North River – was much on the minds of the leaders of the Continental Army. In fact, John Adams identified it as the “key to the whole continent.” Especially after the fall of New York City in the autumn of 1776 to General William Howe, keeping the downstate British forces from joining up with General John Burgoyne’s army holding Quebec – and thereby cutting off Boston by land – became a high priority.
The Americans had already begun building forts and batteries at various points along both banks of the Hudson, but British ships could easily slip by, especially under cover of darkness. Blocking the river’s channel itself was an idea first broached in a 1775 report by General James Clinton and his brother-in-law Christopher Tappen, and in late 1776, two New York members of the Continental Congress’ Committee of Safety, Henry Wisner of Goshen and Gilbert Livingston of Poughkeepsie, conducted soundings of the Hudson riverbed to determine the most workable and strategic locations for the placement of chains, booms and chevaux de frise. The idea was to slow the passage of British boats enough that they could be pounded to bits by cannon and mortar fire from the shores, or forced to turn back.
George Washington turned to Captain Thomas Machin, an artillery officer and engineer who had worked at canal-building in his native England, to plan and install obstacles to upriver passage. The first was a row of chevaux de frise stretching underwater from Fort Lee on the New Jersey side of the Hudson to Fort Washington in northern Manhattan. A cheval de frise is a relatively crude affair, developed in ancient times for terrestrial use in deterring cavalry charges. You’ve probably seen them in movies: a wooden contraption in a three-dimensional elongated X shape, or perhaps merely a large log, with spears or sharpened sticks bristling outward. Modern warfare still used them as late as World War II, covered with barbed wire. Concealed in a riverbed, they’re meant to poke holes in the hulls of ships.
But chevaux de frise are a passive, short-term form of defense, difficult to reposition once dropped in the water, which will quickly rot the wood superstructure. The first line sunk in place in the lower Hudson in 1776 proved not much of a deterrent, since a spy informed the foe of the location of the gap left for the passage of American craft; and in November, both forts fell into British hands. Construction of a second chevaux de frise barrier was begun between Plum Point and Pollepel Island (site of Bannerman’s Castle), north of West Point, but abandoned in 1777 as plans ripened for more ambitious defenses: doubled lines of floating chains and wooden booms.
Captain Machin first installed a chain from Fort Montgomery, at Popolopen Creek at the southern gateway to the Hudson Highlands, to Anthony’s Nose on the east bank in 1776-77. The British didn’t even bother to try to ram their ships through it; they simply landed and overpowered the garrisons of the nearest forts, Montgomery and Clinton, in October 1777 and dismantled the chain. British General Henry Clinton then sailed on upriver, making sure to stop in Kingston along the way and set whatever was flammable in the then-state capital on fire.
Wounded in battle, Captain Machin set to work on a new, sturdier chain as soon as he recovered. The one at Fort Montgomery had been difficult to maintain due to wear and tear from the estuary tides; during its brief lifetime, one of the links broke and had to be reset. So a site further upriver was chosen for the next barrier, at a more defensible location – and one where shipping already had to tack and slow down because of the sharp, canyonlike S-curve in the river, not to mention marshes, shoals and a large island to the east. Reversing tides, currents and prevailing westerly winds off the Highlands made passage even more difficult. The fact that West Point became the dominant fortification in the Hudson Valley in the later years of the war, and evolved into the site of the US Military Academy, was arguably a direct result of its selection as the place to anchor the western end of the Great Chain.
So tight is this riverbend that the Great Chain stretched 600 yards not east to west, but south to north, ending at Constitution Island, which was studded with artillery emplacements that could fire in three directions. Estimated to weigh between 75 and 80 tons altogether, the two-foot-long, 114-pound iron links were forged in Orange County – some sources say at Sterling Forest, others in Warwick – hauled overland on sledges by oxen teams and affixed ten at a time to 16-by-12-foot log rafts. These were floated out into the river, and then the sections were joined by additional links, swivels and clevises. It took about six weeks to install, in the spring of 1778.
The Great Chain could be dismantled and pulled ashore in winter, when the Hudson wasn’t navigable anyway, to protect it from being smashed apart by tide-tossed icebergs. Its placement in the river could also be adjusted using a pulley system. Just downriver, a second barrier of wooden booms was floated, making it nearly impossible for a ship to get up enough momentum to break through the chain – although the notorious traitor Benedict Arnold had advised the British that they could, when he handed over the plans to the fortification at West Point. They never tried.
The Great Chain remained in place until 1782. After the war, it was dismantled, with some of the structure allowed to sink in the river. Most of links were retrieved and melted down at the West Point Foundry in Cold Spring, and a few enshrined for posterity at a variety of Revolutionary War memorials. You can see 13 links at West Point’s Trophy Point, and other segments of chain at Boscobel House and Gardens in Garrison, the New York State Museum in Albany and Raynham Hall in Oyster Bay: the home of Robert Townsend, a spy for Washington and the cousin of ironworks owner Peter Townsend. It’s said that several less-than-scrupulous military surplus traders, including Francis Bannerman, sold counterfeit links to gullible collectors.