The Bessemer Process was the first inexpensive industrial process for the mass-production of steel from molten pig iron prior to the open hearth furnace.The key principle is the removal of impurities from the iron by oxidation by blowing air through the molten iron. The oxidation raises the temperature of the iron mass and keeps it molten. Such processes using air to purify iron had been used outside of Europe for hundreds of years, but not on an industrial scale- the process had existed since the 11th century in East Asia.

The modern process is named after its inventor,Henry Bessemer, who took out a patent on theprocess in 1856. The process allowed for such projects of industrial scale, including the creation of railroad lines. One of the first Bessemer steelmaking operations appeared in nearby Steelton, PA in 1895.