Blast furnace number 7 of the Carrie Blast Furnace.
This mammoth structure once melted all the raw ingredients into molten steel. The Carrie Furnaces were built in 1884 and they operated until 1982. During its peak, the site produced 1,000 to 1,250 tons of iron per day and employed close to 5,000 (!) people. All that is left of the site are furnaces #6 and #7, which operated from 1907 to 1978.