If you are looking at an image that contains multiple documents with unusually neat penmanship, you are looking at a letter book. Letter books are simply copies of original letters bound together in a book and usually organized chronologically. Making such hand written copies was the job of a clerk. Among many other qualities, clerks had to have good penmanship. That’s why these letters are so easy to read.
There are numerous letter books in the Papers of the War Department collections. The letter books of Generals such as Anthony Wayne, for example, furnish us a picture of his Fallen Timbers campaign-both in terms of what he sent to the War Department and what he received from Henry Knox. The letter books of accountants such as Joseph Howell and William Simmons have thousands of entries.
You might have wondered, if there was such a devastating fire at the War Department, where did all these documents come from? One of the reasons is letter books. Recipients kept copies of letters received from the War Department. So, while perhaps the original copy (and the letter book) in Philadelphia might have gone up in flames, a copy of the letter was sometimes recovered elsewhere. And it was for just that reason-having copies of documents in case the originals were lost-that letter books were designed.