Centre Furnace first went into blast and began making iron in 1792. When profits fell, the operation closed in 1809 and did not reopen until 1826. The original furnace was replaced in 1846 by this stack, which could produce as much as 1,500 tons of iron per year and operated until 1858. Workers used a ramp from the hill north of the furnace to reach the top of the 35-foot-tall stone stack and layer iron ore, charcoal, and limestone inside. A water wheel powered by Thompson Run drove bellows that blew air into the bottom of the original furnace in a process known as cold blast. In 1847, the remodeled furnace became hot blast when heated air was recycled instead of escaping through the top. Charcoal heated the furnace to more than 2,600 degrees Fahrenheit, and molten iron flowed into sand molds in the casting house. A main pool of iron branched into smaller pools that resembled a sow nursing piglets, giving rise to the term pig iron. After the iron cooled, men separated it into pieces. Some of it went to local forges, where it was reheated and pounded to remove impurities and make it more malleable, producing wrought iron. Pig and wrought iron traveled by mule, packhorse, wagon, or flat boat to Philadelphia, Pittsburgh, or Baltimore. The metal made at Centre Furnace and other regional ironworks became known as Juniata Iron, and Centre and surrounding counties remained the nation’s leading iron-producing region from 1800 to 1850.