A friend and I kayaked from the river's head at Lake Pymatuning Dam (near Jamestown PA and in Pymatuning State Park) to Greenville, PA. About 6 river miles, I'd guess.
The river tends to get low in the late summer, as releases from the dam are reduced. This summer being cool and wet, the river has been bank full most of the time. We thought we'd "explore" it for a lazy summer afternoon. My expectation was a flat, relatively uninteresting paddle.
As it turns out, the river is a mess. We had to work around at least 25 trees fallen completely across the river, bank to bank. Some we could pick (fight) our way through; some had a sneaker at the bank; other times we had to portage around. Both of us took a wet exit once. Most of the down trees had debris piled up against them, or pulled a few other trees down with them when they fell.
But for a few bridges, and a few homes at the beginning through tiny Jamestown, there is very little evidence of civilization...the woods are beautiful and empty, lots of ducks and big heron. Worst thing was I lost my 49er hat on a branch
The takeout is at a nice city park in Greenville with rest rooms and shelters.
But: unless you are a glutton for punishment, stay away. In a canoe, it is virtually impossible.
Good practice avoiding strainers, though...not enough current to be truly dangerous, yet gives you a good taste of the problems they create. In very high water, it might risky.
The park has the usual washrooms and picnic facilities. Same at the other end, the city park in Greenville. Both towns have groceries, gas, etc.
Put in at the base of the dam in Pymatuning State Park. Jamestown, PA is in the NW corner of PA, about 35 miles south of Erie, PA. Take Hwy 322 west from I-79 at Meadville, PA.
Bring a chainsaw ;)