The illegality of bloomeries is limited to the colonial era when the Crown required American colonists to buy all of their iron needs from the mother country instead of making their own. However, shipbuilders in the New World could not wait until a shipment of British iron fittings arrived, so they operated bootleg bloomeries, using bog iron ore to produce the iron parts they needed to complete the ships sitting on the stocks.
Best regards,
Jerseyman
Just last night I read something on this in James Moore Swank's
History of the Manufacture of Iron in All Ages, published in 1892 on behalf of the American Iron and Steel Association. It has an
excellent section on pinelands furnaces and forges, but this episode occured in Boonton around 1770, not far from where I live.
"Mr. Halsey furnishes us with the following episode in the history of the Old Boonton slitting mill: 'A slitting mill was erected at Old Boonton, on the Rockaway river, about a mile below the present town of Boonton, in defiance of the law, by Samuel Ogden, of Newark, with the aid of his father. The entrance was from the hillside, and in the upper room first entered there were stones for grinding grain, the slitting mill being below and out of sight. It is said that Governor William Franklin visited the place suddenly, having heard a rumor of its existence, but was so hospitably entertained by Mr. Ogden, and the iron works were so effectually concealed, that the Governor came away saying he was glad to find that it was a groundless report, as he had always supposed.'"
The main reason for slitting mills was to cut bar iron into rods for use in nail-making, which were critical to shipbuilding at the time.