The steel plow was invented by John Deere.
The first practical plow was invented by Charles Newbold in New Jersey, in 1797. His cast iron plow was further improved upon by Jethro Wood of New York state. Wood received patents in 1814 and 1819 for his three piece cast iron plow. The three replaceable parts were the moldboard, the share which cut the furrow, and the landside which guided the plow itself. However, the thick, sticky soil found further west of the country stuck to the moldboard, making the plow less effective.
To improve upon the current plow model, John Deere initially experimented with a broken steel saw. After chiseling the teeth off the steel saw, Deere apparently used the saw blade to design the first steel plow. Reports have Deere's first steel plows using the saw blade steel for the share and wrought iron for the moldboard. Steel is a durably hard and strong alloy of iron. With the use of steel, plowing became much easier. Deere's procurement of the superior cast plow steel, manufactured by Jones and Quigg Steel Works of Pittsburgh, eventually made his plows more durable and popular. For more information about Deere's process of creating these steel plows, please refer to the links below.