It's hard to tell in the image, but this thing is massive!
According to the sign, "Pittsburgh's first successful blast furnace for making pig iron. Operations began near here, 1859, using Connellsville coke as fuel. The furnace's technology initiated a new era, leading to more advanced furnaces capable of producing huge amounts of iron and resulting in the modern blast furnace. Clinton Furnace played an important role in establishing Pittsburgh's dominance in iron and steel making. Operations ended in 1927." – PA Historical and Museum Commission 2003
