Rolling and Slitting Mill at Saugus Iron Works National Historic Site

Note: Saugus Iron Works is a modern name. When in operation, the iron plant was called Hammersmith, and it was located in Lynn, Massachusetts. The town of Saugus was not incorporated until 1815.

In 1641, English investors put up £15,000 to build an iron works in the Massachusetts colony. This was enough money to build a facility as big as any in Europe and just as technologically sophisticated. Furthermore, this was to be the first integrated iron works. Most iron works in the 1600s only consisted of a blast furnace for producing cast iron, called pig iron. This was then sold to other companies that refined it into wrought iron, a stronger product with less carbon content that was used to produce durable tools. The wrought iron bars—called merchant bars because they were ready for sale to merchants—were then sold to blacksmiths and other companies that made finished iron products. Some early iron works might also have a finery forge for refining the cast iron into wrought iron, but no final products were made other than merchant bars.

At Saugus, not only was there a blast furnace and a forge, but there was also a rolling and slitting mill that could take merchant bars and produce nail rods and flat iron plates of various thicknesses and lengths that blacksmiths could directly use to make tools, wagon wheels, nails, and other iron products. There were only a dozen such mills in the entire world at the time. (About twelve percent of merchant bars made at Saugus were used for flats and nail rods. Merchant bars were still the main product.)

Flats were created by heating a merchant bar to soften it, then running it through a rolling press to flatten it. The press could be adjusted to produce iron plates of different lengths and thicknesses. The flat bar could then be turned into a saw blade, axe head, or wagon wheel, among many other products. The press, like all other machines at Saugus Iron Works, was powered by a waterwheel.