The Maryland iron industry prospered after the Revolution. The Principio works were taken over by the Maryland General Assembly in 1780. Even so, Thomas Russell II stayed on as ironmaster. His records show the production of "seventy-six barshot, 2900 grapeshot, 2274 two-pound and three-pound cannonballs, 2439 four-pound, 2088 five-pound and six- pound, 1148 nine-pound, 570 twelve-pound and 942 eighteen-pound cannon-balls." The Washington family still retained its one-twelfth share of Principio at the time of the State confiscation. This share was accidentally included in the seizure, and it took the government of Maryland many years to compensate them (May, 1945).

Russell acquired the North East Forge as his share of the Principio Company in 1781. Col. Sam Hughes eventually took over part of the Principio works in 1790 and continued the production of arms, particularly the manufacture of cannons. His skill and prolific production were duly noted by the British Admiral Sir George Cockburn, who sent a detachment of marines to destroy and burn the iron works on 4 May 1814 (Muller, 1963). His cannons and the Americans, however, successfully defied the British at Fort McHenry on Whetstone Point, one of Principio's iron-mining properties. It was that defense that became celebrated and legendary when Francis Scott Key wrote the "Star-Spangled Banner" about the battle.

After the iron work's destruction towards the end of the War of 1812, the iron story shifts away from Principio, which was crippled by the raid, to other production facilities in Maryland.

Various Maryland iron works manufactured domestic and military products throughout the Mexican and Civil Wars. Among these was Muirkirk, which figures prominently in the next part of the story.

Figure 6.— (b) sketch of Muirkirk Iron Works as it appeared in 1863;

During this time there was an increase in the demand for iron for the railroad building, which was booming. Significant profits were to be made, as records from 1839 indicate that pig iron sold for up to $75 per ton but cost only $24 per ton to produce. Production of iron went from 3,165 tons in 1830 to 30,000 tons in 1855. From 1855 to about 1860, there were the beginnings of a decline, which was temporarily halted by the demands of the Civil War (Fig. 6b) but continued thereafter because of the increasing ease of importation of ores by rail and sea, both domestic and foreign. By 1905 the only active furnace was Muirkirk, which continued production until 1920 under ironmaster Ellery F. Coffin, the third generation of Coffin owners (Singewald, 1911; Barnwell, 1925; Payne and Baumgardt, 1990).