"Clark's Memoir" and the "Letter to Mason" are, perhaps, the chief documents for a history of the conquest of the Northwest, though "Bowman's Journal" is much drawn upon and various diaries and official letters are tributary. A full collection of these, edited by James Alton James, of Northwestern University, constitute Volume VIII of the Collections of the Illinois State Historical Library. There are too many of them to be considered here, but a few words concerning the three important papers above mentioned may be of interest. Clark's "Letter" and "Memoir" are both long and circumstantial firsthand accounts of his experiences in the western country. The former was written to George Mason, of Virginia, in the latter part of 1779, after the writer had returned to the Falls of the Ohio. Its special value, as compared with the "Memoir," is that the events were then freshly in mind, whereas the last-named narrative was penned ten or twelve years afterward and is supposed to have been drawn largely from memory. The first account, being privately addressed as a letter, was lost to the world and was not brought to light for years, even Clark being unable to locate it when engaged with the "Memoir." Eventually it was unearthed and first published in 1869. The original is in possession of Judge James Pirtle, of Louisville (as stated by Mr. James in 1912).

The "Memoir," or most of it, seems to have been written in 1790, and was done at the solicitation of Thomas Jefferson and James Madison, who saw the importance of securing, before it was too late, a first-hand account of great events by the chief actor in them. At that time Clark was soured against his fellow countrymen and seems, form his correspondence, to have been a little loath to accept the talk, but once in it his interest carried him through an interesting and valuable piece of autobiography. The original manuscript is in the possession of the Wisconsin Historical Society.

Bowman's Journal was a daily diary of the Vincennes campaign from its organization at Kaskaskia and continuing to the 20th of March, nearly one month after the reduction of Fort Sackville.

These documents are printed in full in W. H. English's "Conquest of the Northwest," the fullest study we have of the life of George Rogers Clark. The volume by James Alton Clark, above referred to, is the fullest collection of all papers relating to Clark.