When I set up this web page, though, I discovered that there was no mention of the Horn hoax anywhere on the Internet, not even at http://www.cyndislist.com. (More recently, sites are starting to appear, such as http://wchspa.blogspot.com/2012/06/mysterious-horn-papers.html) So I trundled back to my local library, and did the research for you. Consider this evidence that, although you can certainly benefit genealogically from the Web, you still must use books and libraries and onsite investigations to truly research your family.
From Gordon Stein's entertaining ENCYCLOPEDIA OF HOAXES, Gale Research Inc. 1993--worth a read even aside from this genealogical fraud! (Please note--some of the more exotic sources cited at the end of the article had to do with other "Historical Hoaxes.")
The Horn Papers were early records of the history of the area comprising western Pennsylvania, southeastern Ohio, western Maryland and northern West Virginia, from 1765 to 1795. These papers were written or collected by Jacob Horn and transcribed and edited by his great, great, great grandson, W. F. Horn, of Topeka, Kansas. The papers were published in several newspapers in western Pennsylvania, from 1933 to 1936. W. F. Horn wrote to the editors of several papers, telling them of the great amount of historical material he had about the newspapers' local areas. The newspapers were interested in printing articles by Horn based on the historical papers, especially after he mentioned that he had plates and descriptions of the lost early Pennsylvania towns of Razortown and Augusta Town. No one locally knew exactly where these towns had been before their destruction, so this was welcome information.
As the Papers were published in newspapers, a minority of opposition began to form. So much of Horn's information contradicted what was published in Boyd Crumrine's History of Washington County, Pennsylvania. A number of incidents recounted in the Horn Papers did not look as if they could have happened, or happened as described. When additional documentation was requested, Horn replied that since the material came from his ancestors' papers, no further authentication was required.
The unearthing of several lead plates with symbols on them in 1936, in the exact site the Horn Papers said they would be, greatly strengthened support for the authenticity of the papers. Nobody seemed suspicious of the fact that it was Horn himself who supposedly unearthed the lead plates.
The Horn Papers were finally published as a book. A committee of representatives from the historical societies of Pennsylvania, Maryland, Ohio, Virginia, and West Virginia was set up simultaneously to look into the authenticity of the papers. The committee's report was published in 1946, one year after the papers were published as a book. Its report (as given by history professors Middleton and Adair) faulted the Horn Ppapers on the following grounds: "1) evidences of ineptitude in copying the original manuscripts, 2) anachronisms and doubtful words and phrases, 3) biographical anomalies, 4) historically incorrect or doubtful statements, 5) internal discrepancies, and 6) internal similarities of documents purporting to be of different authorship."
As an example of "impossible" words for an eighteenth century document, the committee mentioned "hometown," "race hatred," and "frontier spirit." The committee pointed out that a diary, which Horn's records were considered to be, would have to be true throughout, although it did not have to report every event. The writer might be misinformed about something, of course, but "an authentic diary would under no circumstances record the appearance and activities...of a person...known to have been elsewhere or...known to have died." There are many such irregularities in the Horn Papers. An example would be the case of Christopher Gist, who is mentioned in the Papers until his death in 1769. It is known, however, from unimpeachable courthouse death records that Gist died in 1759. Further, when the few papers reputed to be originals (not copies) were examined by document experts, the ink and paper were pronounced to be from the late 1800s. In other words, they were fakes.
And so, the Horn Papers turn out to be a hoax. Why and how anyone would devote so much time and energy to the careful production of such a large mass of fake material is difficult to understand. W. F. Horn never told why he or his agents did the massive forgery.
Bridgeman, William S. "Famous Hoaxes." Munsey's Magazine 29 (August 1903): 730-34.
Gordon, Michael R. "Plant Said to Make Poison Gas in Libya is Reported on Fire." New York Times (March 15, 1990): 1, no. 6: (March 16, 1900); 3 (June 19, 1990): 8.
Horn, W.F. The Horn Papers: Early Westward Movement on the Monongahela and Upper Ohio, 1765--1795. 3 vols. Scottsdale, PA: Published by a Committee of the Greene County Historical Society, by the Herald Press, 1945.
Middleton, Arthur Price & Douglass Adair, "The Mystery of the Horn Papers." William & Mary Quarterly, 4 no. 4 (1947):409-45.
Schumaker, John N. "The Authority of the Writings Attributed to Father Jose Burgos." Philippine Studies 18 no. 1 (1970):3-51.