Just south of the county line the route crosses Torry Run, a tributary of Conneauttee Creek, twice.

North of the county line, PA 99 crosses the creek once more and follows the waterway into the borough of Edinboro.

The route continues northward, following the eastern edge of Edinboro Lake for a short distance.

Near McKean, PA 99 begins to parallel Interstate 79 as both roadways approach the city of Erie.

In 1928, the PA 99 number was first assigned to what is now Pennsylvania Route 5 along the shores of Lake Erie.