Control of the Hudson River was important strategically during the American Revolution. The river, along with lakes George and Champlain, was a potential invasion route from Canada. It also was a physical separator of the colonies. Men as well as supplies crossed the river. To split off the northern colonies from the South and interrupt this supply line was a war-long British ambition.
Engineers, especially engineers with experience, were scarce in the revolutionary forces. Often amateurs stepped forward with plans and schemes to enable the Patriots to obstruct the river. These ideas included fire ships, the sinking of old hulks to impede river traffic and the deployment of chevaux de frise. Chevaux de frise were devices used effectively in the Delaware River to protect Philadelphia. These consisted of iron tipped logs set at an angle and firmly attached to large rock-filled boxes on the river bottom. Ships could not go over these obstructions without ripping out their bottoms or becoming grounded upon them.
The Hudson however is a far mightier river than the Delaware and proved much more formidable than the amateurs who attempted to control it. At the upper end of Manhattan Island, between Fort Washington on the Manhattan side and Fort Lee on the New Jersey side of the river (roughly where the George Washington Bridge now stands), the depth of the shipping channel is between 18 and 50 feet. The channel itself is over 2400 feet wide which makes almost any sort of obstruction at this point impractical.
After much discussion it was decided that the Royal Navy could be prevented from going up the river by placing an immense iron chain from Fort Montgomery on the west bank to Anthony’s Nose on the east. Anthony’s Nose is downstream from West Point and is the location of the east end of the present Bear Mountain Bridge. Many of the links for this chain had already been forged for various smaller projects but never used.
Captain Thomas Machin, an artillery officer, was ordered to handle the project by General Washington who described him as having “just returned from overseeing the Works at Boston; he is as proper a person as any I can send, being an ingenious faithful hand, and one that has considerable experience as an Engineer.” Although he had no formal training as an engineer he had been used on a variety of defensive works in the past. He was practical and had common sense. As it turned out Machin was a good choice.The Fort Montgomery chain was made of 1 ½ inch square and 2 inch square wrought iron bars bent into shape. It was 600 yards long. To stretch such a horrific amount of iron across such a large river, which had not only the normal river flow but also tides, was an incredible undertaking.
The chain was kept on the surface of the river by placing it across numerous log rafts. It was positioned in November 1776. To the horror and disgust of onlookers the chain immediately broke as the pressure of the water was too great for the chain to withstand. Laboriously, the chain was reconnected only to break again. With winter approaching, the chain and its raft floats were removed as the river would soon fill with ice so there would be no danger from the British.
In early April 1777 the chain was again stretched across the river on its log-raft floats. This time it was positioned at a steep angle to the current which, it was hoped, would alleviate some of the pressure from the water. It was a massive thing to behold weighing 35 tons. It was protected by heavy cannons on either shore to prevent the British from attacking and cutting the chain.
On October 6, 1777 the British attacked. However, they did not directly assault the chain. They landed infantry downstream and attacked the forts and river defenses from the rear. Captain Machin was wounded while serving a heavy cannon at Fort Montgomery. When the fort was overwhelmed he and many other Patriots took advantage of the chaos and slipped away into the surrounding woods to safety.
With the Patriot’s defensive artillery under their control the British could safely spend the time necessary to cut through one of the chain links, opening the river to their fleet. They sailed upriver where they burned the town of Kingston, seat of the New York State government.
No sooner had the British gone back down the river than new plans to close the river were investigated. By the middle of January 1778 it was decided that West Point was a better location for a new chain. Up-river traffic makes a sharp turn to the west at West Point. Sailing ships would lose speed and have to tack going around the turn. This would leave them vulnerable to heavy cannon fire from both shores. Infantry would also be stationed nearby to protect the new chain from attack by land. The new chain would be stretched from West Point almost directly North to Constitution Island – a distance of 1500 feet, 300 feet less than the old chain site at Fort Montgomery.
Captain Machin, recovering from his wound, moved ahead with amazing speed. A new chain was required and this chain was to be his chain. The links and parts would be purpose-built solely for the obstruction of the Hudson and would be created to Machin’s specifications. This was the project of a lifetime and Machin was going to make the best of it.
Machin chose the Sterling Iron Works of Chester, New York to forge the chain. Machin had worked with them in the past and was confident they could make his massive chain and the supporting hardware. The chain had to be strong, twice as strong as the Fort Montgomery Chain, yet it had to be light enough that it could be taken up each Fall and installed again in the Spring.
Noble, Townsend & Company’s Sterling Iron Works, run by Peter Townsend, was capable of quality work and also capable of filling such a large order in a hurry. In early February Townsend signed a contract agreeing to supply, “…before the first day of April next …an iron chain…in length five hundred yards, each link about two feet long, to be made of the best sterling iron, two inches and one quarter square, or as near thereto as possible, with a swivel to every hundred feet, and a clevis to every thousand weight [1000 pounds]….” It was a stupendous order requiring over 750 chain links, eight swivels and 80 clevises plus anchors, staples and other hardware.
Townsend, who struggled to maintain a skilled workforce, was constantly losing men to the military draft. He wrangled for an exemption for sixty of his men for a period of nine months. This was far longer than it would take to fabricate the chain. The exemption was included in the contract, reluctantly, as part of the price necessary to get the chain.
The contract also stipulated that Sterling Iron Works would use “their utmost endeavors to keep seven fires at forging and ten at welding” twenty four hours a day.
The specifications for the chain tell much about its design. The measurements were only approximate. Several chain links survive, each of which are of varying sizes and weights. The swivels were installed every hundred feet as the log raft floats were at that distance and the swivel would allow the sections, or sets as they were called, to move without twisting the chain. A “clevis” is a “U” shaped chain link open at one end. Holes were punched near the end of each open end and a large bolt pin passed through the holes. This allowed the sets to be connected with each other. A set consisted of nine links plus a clevis. There were at least 53 sets.
Surprisingly, during the Revolutionary War the United States was producing an astonishing 14 percent of the world’s iron, 30,000 tons. Iron works required huge quantities of wood. English furnaces were having to relocate to areas with a wood supply while the forests of North America were limitless. The colonies boasted 72 cold blast furnaces, plus many smaller forges. Their production was greater than that of England and Wales combined. Each day an acre of forest was consumed while the furnaces were making the iron for the chain.
Nothing like the West Point chain had ever been constructed. It was a mammoth project. A wheel powered by water from Sterling Lake operated a bellows that supplied a continual stream of air through a pipe into the furnace hearth. The furnaces were continually fed with charcoal made from four-foot billets of hardwood. The iron ore, from a thick vein of black magnetite ore of 60 to 70 percent purity, was combined with a lime flux. All of which was dumped down the stack of the furnaces while in operation.
The heat from the fire, enhanced by the pumped in air, reduced the iron ore to molecules of ferrous and ferric oxide and some of the carbon from the charcoal would combine with the iron. The iron making process also produced huge quantities of slag, carbon monoxide, carbon dioxide, hydrogen, methane and smoke. It was a dirty and dangerous business with the furnaces and welding forges going at the same time.
Twice a day molten iron was drained from each hot furnace into channels cut into the earth. The iron in these channels were the “pigs” or ingots. They were from three to ten feet long and four or five inches in thickness. They weighed from 35 to 100 pounds.
When ready for shaping, the pigs were reheated red hot and then wrought through repeated hammerings into “aconies” – dumbbell-shaped iron bars with large square ends. The ends provided the ironworkers a place to grasp the aconies with great tongs to shift the hot iron as it was beaten into shape under a trip hammer.
The trip hammer was a large wooden beam with a cast iron head, powered by a water wheel, that was raised and dropped endlessly to hammer iron against a large anvil. After the aconie was beaten into a long squared section the dumbbell ends were cut off leaving a section of iron roughly 2 ½ inches square and about 5 or 6 feet long. This iron bar would become a chain link. Over 750 of these bars were required.
The bars were heated again to a red hot glow and bent into shape around a huge mandrel after which the ends of the bars were welded together to make a finished link. The swivels and clevises were more difficult to form and required more beating with sledge-hammers.
This process went on for weeks both day and night. The finished product was not much to look at. The links were irregularly shaped and twisted. However, no one could deny it was a mighty chain the likes of which no one on the continent had ever seen before.
After the chain had been made by Sterling it was taken, in sets, on sledges pulled by oxen, to Brewster’s Forge at New Windsor, upriver from West Point for final assembly. Each load consisted of nine links plus a clevis and pin. At Brewster’s the chain was put together by pounding the clevis pins into the clevises to connect the sets. The chain was then attached, by huge staples, to log rafts made up of hundreds of logs, for the trip down the Hudson to West Point.
Finally, the much anticipated day arrived. The chain was ready to be installed. Machin had devised enormous capstans, much like those used on ships for hauling up anchors, powered by teams of soldiers who strained to winch the chain across the river. At each end the chain was anchored to large rock-filled cribs. The log raft floats were 50 feet long and 12 feet wide. The logs were waterproofed with tar and oakum to help keep them from becoming waterlogged. Both ends of the logs were sharpened to give them less resistance to the flowing water. The chain was not stretched tight but rather was loose and curved downstream like a necklace. Large anchors were attached to the chain to help hold it in place. On April 30th Thomas Machin could look at his chain as it stretched across the Hudson with tremendous satisfaction. The labor of hundreds of ironworkers, lumbermen, wagon drivers, river men and soldiers was complete. In eight weeks of sweating, cursing and smashing fingers the great chain had been manufactured, assembled, transported and installed across the river. The entire project was a stupendous engineering feat.
The chain was more than just a huge barrier across the river. An additional engineering curiosity is the probability that there was a way of lowering the chain at the western end to allow friendly ships to pass. A brief diary notation in July 1778 and West Point garrison orders of August 1780 “…to examine every kind of vessel that approaches this garrison and none to go over the chain without they have a passport from the governor of the state” hint at a complexity far beyond a simple huge chain.
The great chain at West Point was never tested by the Royal Navy. It was taken out of the river each fall and replaced again each spring until the end of the war. After the war it was allowed to lie rusting on the shore at West Point for twenty years. When the military academy was established in 1802 the chain was moved to the Ordnance Compound where it spent almost 30 years. In 1829 the chain was sold for scrap. However, a few links were spared and remained at the Ordnance Compound. In 1857 these links were put on display at West Point. They are still there today, twelve original chain links, plus a clevis and swivel resting forever in a place of honor.
 Lincoln Diamant, Chaining the Hudson, the Fight for the River in the American Revolution (New York: Carol Publishing Group, 1994), 41. Diamant cites many obscure primary sources and is the best single account of the Chain.  George Washington to the New York Convention Secret Committee, June 21, 1776.  Diamant, Chaining the Hudson, 95.  Diamant, Chaining the Hudson, 105-106.  Diamant, Chaining the Hudson, 140.  Merle Sheffield, The Chain and Boom, http://www.hudsonrivervalley.org/links/pdfs/chainandboom.pdf, accessed Aug. 30, 2014, 3. Contract between Sterling Iron Works and the Army of the United States.  Sheffield, Chain and Boom, 3.  Diamant, Chaining the Hudson, 144.  Diamant, Chaining the Hudson, 97.  Diamant, Chaining the Hudson, 152.  Diamant, Chaining the Hudson, 148, 155.  Diamant, Chaining the Hudson, 156; Sheffield, Chain and Boom, 7; USMA, History Dept., West Point Fortifications Staff Ride, 36.  Sheffield, Chain and Boom, 7.  Diamant, Chaining the Hudson, 179, 182.