He preserved most of the letters written to him and many of these deal with farming matters.
During part of his career he had a copying press and kept copies of his own important letters, while many of the originals have been preserved, though widely scattered.

When away from home he required his manager to send him elaborate weekly reports containing a meteorological table of each day's weather, the work done on each farm, what each person did, who was sick, losses and increases in stock, and other matters of interest.

Scores of these reports are still in existence and are invaluable.

He himself wrote--generally on Sunday--lengthy weekly letters of inquiry, direction, admonition and reproof, and if the manager failed in the minutest matter to give an account of some phase of the farm work, he would be sure to hear of it in the proprietor's next letter.
Washington's correspondence on agricultural matters with Arthur Young and Sir John Sinclair, eminent English agriculturists, was collected soon after his death in a volume that is now rare.

In it are a number of letters written by other American farmers, including Thomas Jefferson, relative to agriculture in their localities.