Route 77 heads north from Route 49 and County Route 609 (CR 609) in Bridgeton, Cumberland County on Pearl Street. In a short distance, the route intersects CR 670 and then crosses CR 552, which ends a block to the west at Laurel Street. It continues north through residential areas of Bridgeton, meeting CR 665 and CR 659. Route 77 heads into a commercial area, passing under a Winchester and Western Railroad line and crossing into Upper Deerfield Township at the junction with Laurel Plaza Drive. The route intersects the western terminus of Route 56 and CR 622, where the route is briefly a four-lane road. Past this junction, Route 77 heads into farmland, where it encounters several county roads including CR 704, CR 617, and CR 658. It heads north into Seabrook, where it meets CR 743 and CR 711. Route 77 intersects CR 612 and CR 630 before crossing CR 540 in Deerfield. Past CR 540, the route has junctions with CR 640 and CR 730. Route 77 then encounters CR 614, the last county route intersection in Cumberland County.