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Moldboard Plow

Thomas Jefferson had an abiding interest in improving the technology of farming. One of his more important contributions to agriculture was the "mouldboard of least resistance" for a plow.1

Plow with a recreation of Jefferson's Mouldboard of Least ResistanceWhile serving as minister to France, Jefferson had the opportunity to observe European plow designs. Their deficiencies inspired him to set down in a memorandum (1788) his plans for an improved moldboard, the wooden part of the plow that lifts up and turns over the sod cut by the iron share and coulter.2 He wished to make that lifting and turning action as efficient as possible, so that the plow could be pulled through the soil with the least expenditure of force. He brought his love of mathematics to his design, which he declared was "mathematically demonstrated to be perfect."3

By 1794, Jefferson had put his plans into action at Monticello. He had a plow fitted with a wooden moldboard of his design and reported to Sir John Sinclair (March 23, 1798) that "an experience of 5. years has enabled me to say it answers in practice to what it promises in theory." In addition to offering the least resistance as it was pulled through the soil, Jefferson's moldboard had a further advantage: "[I]t may be made by the coarsest workman, by a process so exact, that it's form shall never be varied a single hair's breadth." Ease of duplication was thus another measure of the usefulness of his design.4

In 1814, Jefferson began to have his moldboards cast in iron. He informed Charles Willson Peale (March 21, 1815) that the plow with his iron moldboard was "so light that two small horses or mules draw it with less labor than I have ever before seen necessary. it does beautiful work and is approved by every one."5

Just how widely Jefferson's moldboard was adopted by others is unclear. He never sought to patent it, and in fact sent numerous models to friends at home and abroad, where his design met with general approval. Jefferson's moldboard was featured in James Mease's Domestic Encyclopedia (Philadelphia, 1803), and the French Society of Agriculture awarded Jefferson its gold medal and membership as a foreign associate.6

- Russell L. Martin and Lucia C. Stanton, 10/88

Further Sources

Related Links:
Monticello Plantation Model
Jefferson: the Scientist and Gardener


John Maddox's picture
The way I heard this story, Jefferson and William Cabell did go into business for a while manufacturing and selling this improved plow. They hired a teamster to carry them around to nearby towns. Teamsters name was "John Maddox" presumably a distant relative. I will post the reference if I can find it. //maddox
John Maddox
TomBorkes's picture
Is there any record that estimates the increased efficiency (time saved as a percentage) of Mr. Jefferson "moldboard of least resistance" over the traditional moldboards of the time? Thank you, Tom
Tom Borkes
ejohnson's picture
One of the things that popularly gets said about TJ is that he was a big inventor. At Monticello, we typically will argue that he wasn't so much an inventor as an improver, though we will often say he did invent at least one thing: this "mouldboard of least resistance." I don't want to denigrate TJ's achievements--they are absolutely legion--but I wonder why this one thing gets held out as an invention while other things aren't. It seems to me that this is an improvement like many of his other improvements: he took a thing that was useful already and worked to make it even better. He did it with the polygraph and the great clock. I find myself wondering what is different in this case--why is the moldboard an invention and not an innovation?
Eric Johnson
econan's picture
I have been reading about Jethro Wood of Moravia, NY and his cast iron plow with replaceable parts. I understand that Jefferson examined Wood's plow and wrote him a letter extolling the design. Wood received his second patent in 1819. Would Jefferson's letter be in the Monticello collection? Or any references to Jethro Wood?


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