These do not connect to trails closer to the city, but upriver there are two that come to mind--the Butler Freeport trail and also the Armstrong Trail. The Armstrong Trail traces the south/east side of the Allegheny River north starting at Ford City, while the Butler Freeport Trail goes between those two places.
http://www.armstrongcounty.com/hike.php
http://butlerfreeporttrail.org/
Google's bicycle layer lets you visualize these trails and where they go: https://maps.google.com/?ll=40.849657,-79.516983&spn=0.511605,0.837021&t=m&z=11&lci=bike