In 1788 the first new permanent American settlement northwest of the Ohio River (not including French villages) within the borders of the Northwest Territory was established at Marietta, Ohio. However, American involvement in that frontier region had begun nearly 20 years prior to that, before the Revolutionary War started, with pioneers moving into wilderness areas on the edge of the Northwest territory. These lands were east and south of the Ohio River, in present-day western Pennsylvania, West Virginia, and Kentucky.
This site has a number of early books about that frontier, authored by people who had lived there. Each of the books below combine first-person accounts with anecdotes the authors collected, to describe life on the frontier and to portray some of the most memorable characters and events.
Doddridge, Joseph, Notes, on the Settlement and Indian Wars, of the Western Parts of Virginia & Pennsylvania (etc) (1824)
Finley, James B., Autobiography of Rev. James B. Finley; Or, Pioneer Life in the West (1853)
McClung, John, Sketches of Western Adventure (1832)
McDonald, John, Biographical Sketches of General Nathaniel Massie, General Duncan McArthur (etc) (1838)
(in the Collective Biographies section)
Hildreth, S. P., M.D., Biographical and Historical Memoirs of the Early Pioneer Settlers of Ohio with Narratives of Incidents and Occurrences in 1775 (1852)