According to the Descriptive Pamphlet put out by the National Archives and Records Administration, which houses the original correspondence, these are volumes 20-22 of the personal copybooks of George Washington's correspondence from 1789-96. The remainder of the volumes are at the Library of Congress.
These are handwritten copies of letters to and from George Washington, so the signatures are not original. Most of the letters involve Secretaries of State John Jay, Thomas Jefferson, Edmund Randolph and Timothy Pickering. Topics range from the new dollar (and subsequent theft of equipment and metal from the Mint - 16 Oct 1794), forcing peace on the Barbary States (12 July 1790), the jailing of a post rider, and the itinerary of Washington's tour to Savannah. GA. Since the government was young and relatively uncomplicated, the correspondence reflects simple details. The handwriting is different as well, and may be difficult to read initially. The biggest difference is how they wrote the letter "s". It looks almost, to us, like a cursive "f".
At the beginning of the correspondence is an alphabetical index by name or topic indicating page numbers where the letter can be found. This index is for Volume 20 only. The other volumes are arranged chronologically. You can see an example of one of the letters by clicking on the image to the right. This letter, from George Washington to Thomas Jefferson at Mt. Vernon dated 1 April 1791, concludes with Washington's itinerary on his southern tour. It is interesting to note that, prior to this paragraph, Washington offers Jefferson some maps that Gen. Knox may have; if not, they may be in Washington's study in Philadelphia. Image that happening today!