There's definitely plenty to see out there not all of it is going to be handicap accessible. Its worth checking out.
An observation deck for the main falls is wheelchair accessible, but others have a few steps. The segment of the Great Allegheny Trail that runs from Ohiopyle to Confluence is paved, but this is the mountains, so there are ups and downs along the way. Cucumber Falls and the natural water slide are not accessible. You can sort of see these from the top, but there are a lot of steps over natural, uneven ground to see the full effect.
The visitors center is handicapped accessible (call to make sure it's open though) and the area outside by the falls is accessible. I don't remember if there was an area that would take you right down by the water's edge, but you can see everything from the biking, running bridge up river. I saw someone in a wheelchair on the bridge, but don't remember if they were being pushed or moving on their own power. Definitely worth a trip. Call the Ohiopyle Visitor Center for more information.
No wheelchair access to some of the waterfalls and river. I'm under the impression, where they launch out, to the rapids, there's access. Wheelchair access, is throughout the town.
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