From there, PA 412 continues into Northampton County and passes through Hellertown before coming to an interchange with Interstate 78 (I-78) and heading into Bethlehem.

The route continues through a mix of farmland and woodland with some development, passing through Bucksville and heading to the southwest of Palisades High School.

[2][3] The route enters Lower Saucon Township in Northampton County, which is in the Lehigh Valley, becoming Leithsville Road and running through more rural areas.

PA 412 enters the borough of Hellertown and becomes Main Street, a three-lane road with a center left-turn lane that runs past businesses.

PA 412 passes over the Lehigh Valley Rail Management line before turning northwest onto four-lane divided Daly Avenue.

The route passes between the Wind Creek Bethlehem casino resort to the north and residential neighborhoods to the south, curving west.

The road intersects the south end of the Minsi Trail Bridge, which carries Stefko Boulevard across the Lehigh River.

A short distance later, the route turns southwest onto Broadway and passes through urban areas of homes and businesses.

[9] In March 2012, a project began to widen PA 412 between Cherry Lane in Hellertown and Daly Avenue in Bethlehem.