Route 654 begins at an intersection with Route 44 in Limestone Township, just east of the hamlet of Oval. Route 654 proceeds to the northeast through several farms and leaves Limestone for Bastress Township, and almost immediately enters the hamlet of Bastress. After the intersection with Jacks Hollow Road, the route curves from the northeast to the northwest before an elongated curve back to the northeast north of the hamlet. At the intersection with Dincher Lane, Route 654 turns eastward, leaving the clearings for a dense woodland that contains another curve, this time to the north. After making this curve, the highway enters the hamlet of Nisbet, in Susquehanna Township. Unlike the forests that precede it, Route 654 through Nisbet is a stretch of residences on both sides of the highway. After making a curve to the east, the right-of-way merges with nearby East Village Drive, where the name of the road changes to Riverview Drive. At this point, Route 654 parallels the West Branch of the Susquehanna River and nearby railroad tracks. After the merge, the route returns to its wooded setting for several miles along the West Branch. After entering Armstrong Township, Route 654 forks to the southeast as Euclid Avenue, as the right-of-way continues as Cochran Avenue. Both roads enter the borough of Duboistown. Route 654 crosses through downtown, passing businesses on the west side of town. At the intersection with Arch Street, Route 654 is provided a connection to the city of Williamsport. After the intersection with Arch Street, Euclid Street continues further into downtown Duboistown, crossing through the center of town before intersecting with Riverside Drive and entering the community of South Williamsport. Paralleling U.S. Route 15 on the opposite side of the river, the route soon intersects and merges with West Southern Avenue, which becomes to the route moniker through South Williamsport, passing local businesses and homes. At the intersection with South Market Street, Route 654 intersects with the southbound lanes of U.S. Route 15, which had just crossed over the Susquehanna. The PA 654 designation ends at South Market Street, but Southern Avenue continues as SR 2012 to meet the northbound lanes of US 15 at Hastings Street.
