Everything Needs Iron

The key to the industrial boom is the combination of machines, fuel and transportation. Factories can't produce anything in bulk without machinery, and can't reach widespread customers without rail connections.

All this requires quantities of iron far beyond previous needs. Railroads need rails, locomotives and bridges. Machines need shafts, gears and rigid iron frames. Steam engines supply the power.

Coal becomes the new fuel. Railroad lines into rich Pennsylvania coal fields enable the production of iron in much greater quantities. Additional iron ore is shipped in from newly-discovered deposits in upper Michigan.
Iron and coal, 1870 map

  Industrial Twins
RED zones on the map are regions containing scattered deposits of iron ore, while GRAY indicates coal. Both are needed in large quantities to produce iron. The natural center for the iron industry is Pennsylvania, which has ready access to both. Pennsylvania also has deposits of a special kind of super coal, much harder than the coal found elsewhere.

Cast iron

  Hard but Brittle
The iron that flows out of a blast furnace is brittle, because it naturally contains small amounts of carbon. Such iron is very hard, but only suitable for molding into items which will not be subject to bending. Cast iron doesn't bend. It cracks. That's why you can break up a cast iron stove by hitting it with a sledgehammer. The items shown above are typical cast iron products. Most other iron products, however, require a less brittle form of iron, which will flex somewhat under stress, without cracking.


Wrought iron

  Working the Iron
Wrought iron is made by cooking out most of the carbon. This results in metal that is remarkably flexible, when softened. It can be beaten into simple shapes even when cold, but bends and flows much more easily when heated to cherry red. The simplest example is a horseshoe, formed over the blacksmith's anvil (left). Industrial use of wrought iron rises dramatically after the Civil War (top right). Wrought iron sheets can be rolled into curves, and then riveted together to form steam boilers (bottom center).