In the 1790s, Thomas Jefferson and other Virginia tobacco growers began to diversify by planting wheat. Their timing coincided with the development of the threshing machine, designed to remove a plant’s grain from its stalks and husks, thus “separating the wheat from the chaff.” The first threshing machines were invented in Great Britain in the 1780s and American-made machines soon followed.

Jefferson’s fellow planter, George Washington, was making the same transition to wheat, and both men were interested in learning about the new technology. In August 1791, President Washington and Secretary of State Jefferson jointly visited a farm, southwest of Philadelphia, to see a threshing machine in operation.[1] The locally-made machine, developed by Alexander Anderson, was a drum-and-beater style at the farm of Samuel Powell, president of the Philadelphia Society of Agriculture.[2] 

After the visit to Powell’s farm, Jefferson learned more about threshing machines through a 1791 issue of Arthur Young’s semi-annual Annals of Agriculture.[3] Young was an English writer well known for supporting agricultural improvements. Upon reading Young’s article, concerning a machine based on Scottish designs, Jefferson took action. He wrote to Thomas Pinckney, recently appointed as minister to Great Britain, asking him to secure a model of the Scottish machine.[4] 

Pinckney tracked down a machine near London and employed a mechanic to fulfill Jefferson’s request.[5]

By December 1793, Jefferson’s model had arrived in New York and was on its way to Richmond and then Monticello.[6] Jefferson wrote in his memorandum book on December 12, “Gave order on bank US. for 62.8 to John Vaughan for his bill for £13–13 sterl. on Byrd, Savage & Byrd paiable to T. Pinckney, and inclosed it to T. Pinckney to pay for threshing model.”[7]

Though Jefferson sent his first harvest of wheat to market in 1793, it was not until the summer of 1796 that his first threshing machine was built. He hired John Buck to do the work, based on the British treble-geared model, but later made modifications by substituting whirls and bands for the gears.[8] When the harvest season was completed, Jefferson was able to report that the new machine operated “with perfect success.”[9] By 1813, Jefferson owned three threshing machines. Two were portable, driven by horses, and one was stationary, driven by water.[10]

Wheat remained the primary export crop at Monticello until Jefferson’s death in 1826.

- Nancy Verell, 8/31/15

Primary Source References

10 February 1793. (Thomas Pinckney to Jefferson) “After many inquiries I have found one of the threshing Machines at no great distance from this City. I went to the place where it is and prevailed on the owner to let me see it work. I liked the performance so well that I have engaged a Mechanic to make a compleat model of it and hope to send it you in good time for you to have one erected to thresh out your next crop. With the force of three horses to work it and three men to feed and attend it from 8 to 16 bushels of Wheat are threshed by it and other grain in proportion. This account I received from the owner having only seen a few sheaves threshed.”[11]

12 April 1793.  (Jefferson to Thomas Pinckney) “I shall thank you most sincerely for the model of the threshing machine, besides replacing the expence of it. The threshing out our wheat immediately after harvest being the only preservative against the weavil in Virginia, the service you will thereby render that state will make you to them a second Triptolemus.”[12]

21 April 1793. (Jefferson to Thomas Mann Randolph) “Mr. Pinkney has seen the Scotch threshing machine. He says that three men and three horses get out from 8. to 16. bushels an hour. He promises I shall have a model in time to get out the crop of this year.”[13]

19 May 1793. (Jefferson to James Madison) “I expect every day to receive from Mr. Pinckney the model of the Scotch threshing machine .... Mr. P. writes me word that the machine from which my model is taken threshes 8. quarters (64. bushels) of oats an hour, with 4. horses and 4. men. I hope to get it in time to have one erected at Monticello to clean out the present crop.”[14]

11 August 1793. (Jefferson to Thomas Mann Randolph) “I found considerable hopes on the threshing machine expected, as 4. horses suffice to work that, and I had proposed to work my ploughs with oxen. Should that machine fail, more horses must be kept for treading wheat in the proper season ....”[15]

ca. 28 August 1793. (James Adair to Jefferson) “... I have just arrived here in the Ship Amsterdam Packet, after a passage of 68 days from London. ... I shall have the honour to bring with me a box addressed to you, Sir, (of which the key is inclosed in a letter from Mr. Pinckney, which, on recollection I have thought right to transmit herewith) containing the model of a threshing mill. I have accidentally discovered that the person who made it, and who seems an ingenious Millwright, came on board the same Ship with myself as a Steerage passenger, with a view to settle in America. ... If you direct me, Sir, I shall send the model immediately that you may be enabled to form some idea of his abilities."[16]

1 September 1793. (Jefferson to James Adair) “I ... am very thankful ... for your attention to the threshing machine, which, if it answers what I have heard of it will be a vast acquisition to the states of Virginia and North Carolina. If you should not be coming on yourself to Philadelphia in the course of the present week, and could take the trouble of finding some careful gentleman coming in the stage, and who would be so kind as to take charge of the machine, or if you will be so good as to deliver it to Mr. Remsen ... it will oblige me. ... A very peculiar circumstance in all the country South of the Patowmac, the finest wheat country in America, renders such a machine as valuable as the discovery of the grain itself.”[17]

29 January 1794. (Thomas Pinckney to Jefferson) “I wish the threshing machine may answer the purpose, I have no doubt that on a proper stream of water the effect of it would be astonishingly great ....”[18]

8 September 1795. (Jefferson to Thomas Pinckney) “The beginning of our year promised great crops. That of wheat has been good. But those of corn and tobacco are much injured, indeed almost ruined, by such continual floods of rain as were never before known. This circumstance too, preventing our treading out our wheat, which is generally done in the open air, exposes that much at this moment to the weavil. It has determined me, before another harvest, to prepare a threshing machine on the model you sent me, which the variety of other things wanting in my farms on my return to them, has as yet prevented my making.”[19]

5 January 1796. “Mr. Buck begins to work.”[20] 

6 July 1796. (George Washington to Jefferson) “If you can bring a moveable threshing Machine, constructed upon simple principles to perfection, it will be among the most valuable institutions in this Country; for nothing is more wanting, & to be wished for on our farms.”[21]

12 December 1796. (Jefferson to Edward Rutledge) “I understand you have introduced the Lieth machine into your state for threshing your rice. I have used one this year for my wheat with perfect success.”[22]

6 November 1812. (Jefferson to Dr. Cunningham Harris) “[W]e cultivate wheat here extensively & solely, and every body is getting the Leith machine for threshing it. I mean the original double or treble geered machine, divested of all those things which have been called improvements, in which the wheat is presented to beaters revolving like the vanes of a wheat fan. I have three of them myself, one going by water, & two by horses. many have them in our neighborhood. those moved by horses get out from 80. to 150. bushels a day with from 2. to 5. horses, & cost from 100. to 150.D. those by water get out 300. bushels a day and more if they could be attended, & cost in proportion to their geer, canals, dams Etc.”[23]

13 June 1815. (Jefferson to Charles Willson Peale) “Our threshing machines are universally in England fixed with Dutch fans for winnowing, but not with us, because we thresh immediately after harvest, to prevent weavil, and were our grain then laid up in bulk without the chaff in it, it would heat & rot ....”[24]

29 December 1815. (Jefferson to George Fleming) “[T]o a person having a threshing machine, the addition of a hemp break will not cost more than 12. or 15. D. you know that the first mover in that machine is a horizontal horsewheel with cogs on it’s upper face. on these is placed a wallower and shaft which give motion to the threshing apparatus. on the opposite side of this same wheel I place another wallower and shaft, thro’ which, and near it’s outer end, I pass a cross-arm of sufficient strength .... nearly under the cross arm is placed a very strong hemp-break, much stronger & heavier than those for the hand.”[25]

8 May 1816. (Jefferson to Charles Willson Peale) “[I]n a former letter I mentioned to you that I had adapted a hemp break to my sawmill, which did good work. I have since fixed one to my threshing machine in Bedford, which breaks & beats about 80. lb. a day with a single horse. the horizontal horsewheel of the threshing machine drives a wallower and shaft, at the outer end of which shaft is a crank ....”[26]




  1. ^ Washington to Jefferson, August 21, 1791, in PTJ, 22:57. Transcription available at Founders Online.
  2. ^ See Samuel Powell, “American Husbandry,” in Arthur Young, ed., Annals of Agriculture and Other Useful Arts, vol. 17 (Bury St. Edmund’s: Printed for the Editor, 1792): 206-08.
  3. ^ “Communications Concerning Mr. Rastrick’s Threshing Machine,” in Arthur Young, ed., Annals of Agriculture and Other Useful Arts, vol. 15 (Bury St. Edmund’s: Printed for the Editor, 1791): 481-93.
  4. ^ Jefferson to Pinckney, June 24, 1792, in PTJ, 24:119. Transcription available at Founders Online.
  5. ^ Pinckney to Jefferson, February 10, 1793, in PTJ, 25:168. Transcription available at Founders Online.
  6. ^ Jefferson to Robert Gamble, December 8, 1793, in PTJ, 27:494. Transcription available at Founders Online.
  7. ^ December 12, 1793, MB, 2:907. Transcription available at Founders Online.
  8. ^ Jefferson to William Booker, October 4, 1796, in PTJ, 29:187-88. Transcription available at Founders Online. See also MB, 2:946, 2:946n70. Transcription and note available at Founders Online.
  9. ^ Jefferson to Rutledge, December 27, 1796, in PTJ, 29:231. Transcription available at Founders Online.
  10. ^ Jefferson to Cunningham Harris, November 6, 1812, in PTJ:RS, 5:444. Transcription available at Founders Online.
  11. ^ PTJ, 25:168. Transcription available at Founders Online.
  12. ^ PTJ, 25:536-37. Transcription available at Founders Online.
  13. ^ PTJ, 25:581. Transcription available at Founders Online.
  14. ^ PTJ, 26:62. Transcription available at Founders Online.
  15. ^ PTJ, 26:658. Transcription available at Founders Online.
  16. ^ PTJ, 26:775. Transcription available at Founders Online.
  17. ^ PTJ, 27:3. Transcription available at Founders Online.
  18. ^ PTJ, 28:11-12. Transcription available at Founders Online.
  19. ^ PTJ, 28:457-58. Transcription available at Founders Online.
  20. ^ MB, 2:935, 2:935n42. Transcription and note available at Founders Online.
  21. ^ PTJ, 29:144. Transcription available at Founders Online.
  22. ^ PTJ, 29:231. Transcription available at Founders Online.
  23. ^ PTJ:RS, 5:444. Transcription available at Founders Online.
  24. ^ PTJ:RS, 8:535-36. Transcription available at Founders Online.
  25. ^ PTJ:RS, 9:303. Transcription available at Founders Online.
  26. ^ PTJ:RS, 10:32-33. Transcription available at Founders Online.