The American Nation A History of the United States, Combined Volume (14th Edition)

Iron, Oil, and Electricity 461

Iron, Oil, and Electricity

The transformation of iron manufacturing
affected the nation almost as much as rail-
road development. Output rose from
920,000 tons in 1860 to 10.3 million tons
in 1900, but the big change came in the
development of ways to mass-produce
steel. In its pure form (wrought iron) the
metal is tough but relatively pliable: It
bends under great stresses. Ordinary cast
iron, which contains large amounts of car-
bon and other impurities, is hard but brit-
tle. Steel, which contains 1 or 2 percent
carbon, combines the hardness of cast iron
with the toughness of wrought iron. For
nearly every purpose—structural girders
for bridges and buildings, railroad track,
machine tools, boiler plate, barbed wire—
steel is immensely superior to other kinds
of iron.
But steel was so expensive that it
could not be used for bulky products until the inven-
tion in the 1850s of the Bessemer process, perfected
independently by Henry Bessemer, an Englishman,
and William Kelly of Kentucky. Bessemer and Kelly
discovered that a stream of air directed into a mass of
molten iron caused the carbon and other impurities to
combine with oxygen and burn off. When measured

amounts of carbon, silicon, and manganese were then

added, the brew became steel. What had been a rare

metal could now be produced by the hundreds and

thousands of tons. The Bessemer process and the

open-hearth method, a slower but more precise tech-

nique that enabled producers to sample the molten

mass and thus control quality closely, were introduced

This 1900 photograph of steel factories at night in Duquesne, near Pittsburgh, was tinted by hand.

Source: North Wind Picture Archives.

Electric companies advertised the advantages of electric lights at regional exhibitions,

such as these electrified renderings at the 1897 Tennessee Centennial Exposition. The

lights evoke the Parthenon of ancient Athens and the pyramids of Egypt.