Perhaps Cumberland? Although not in the Ohio Country proper, I think this is as close as you're going to get, right up against the Allegheny Front and predating the French and Indian War.
There was no European settlement in the Ohio Country to speak of before 1750, and only French and British military outposts leading up to the War.
The Ohio Country was the traditional home of the Shawnee, who, although tributaries to the Iroquois, only began leaving the area in the 1730s-1740s because of disruptions from the fur trade.
Some outposts in Western Maryland are the only early European settlements even close to the area. Maryland was able to settle the western area under its charter early because of a purchase from the Shawnee.
The Ohio Company was formed in in Virginia in the 1740s; this company hired Thomas Cresap and Christopher Gist to survey the area, with the assistance of Shawnee chief Nemacolin.
The Fry -Jefferson Map of 1755 tries to show the situation as of 1751:
(A higher resolution image can be found at https://www.loc.gov/resource/g3880.ct000370/)
West of the Alleghenies, the map is not a very accurate survey. For example, Fort Necessity is shown far to the south and west of its actual location. But this shows that the area was not well-known enough to be mapped properly.
A couple of noteworthy points on the map:
- "Shawno", Maryland (Later Oldtown), settled by Cresap in 1741 on the site of an old Shawnee village.
- "Wills Creek", Maryland (later Cumberland), established in 1750 in another old Shawnee village (Caicutuc) which became the base for the Ohio Company, George Washington's reconnaisance of the French forts being built in Northwest PA , and General Braddock's ill-fated expedition against the French in 1755.
- Several circles in what is now West Virginia, between Shawno and Wills Creek, which appear to represent individual settlers' houses.
- a "coal mine" on the Potomac west of Cumberland. Yes, they were doing that even then.
- Logs Town, in what is now Ohio, site of a 1752 treaty between the Ohio Company and the Shawnee.
- Fort Duquesne, which the French built in 1754 after capturing an earlier British outpost. As the French position became untenable, they destroyed Fort Duquesne, and the British later built Fort Pitt (later Pittsburgh) on the site.
- "Gists Settlement", which was northeast of present-day Uniontown on the map. Gist started a plantation here in 1753 but it was desroyed by the French. Don't confuse this with a 19th century gift of land by a different Gist to slaves he freed).
- "Queen Aliquippa's Town", the site of present-day McKeesport (not Aliquippa!), which wasn't settled until 1795.