PA 309 enters Butler Township and becomes South Hunter Highway, heading through forested areas as it traverses Buck Mountain as a two-lane road, gaining a second southbound lane as it descends the mountain. The route turns to the north and runs through a mix of fields, woods, and development as a two-lane road briefly before becoming four lanes. The road heads northeast and runs through forests to the west of Green Mountain, narrowing to two lanes before becoming three lanes with two southbound lanes and one northbound lane. PA 309 bends to the north again and becomes four-lane undivided North Hunter Highway, running through wooded areas with some homes and businesses and passing through the communities of Honey Hole and Edgewood. The route becomes a divided highway and comes to an interchange with I-80. Past this interchange, PA 309 becomes a three-lane undivided road with two northbound lanes and one southbound lane and runs through wooded areas with some residences and commercial establishments, passing by the entrance of the community of Sand Springs. The road curves to the north-northeast and traverses forested Nescopeck Mountain, becoming four lanes as it comes to the summit in the community of Nescopeck Pass and bends north. The route heads into Dorrance Township and becomes South Mountain Boulevard, heading northeast to descend Nescopeck Mountain with one northbound lane and two southbound lanes. PA 309 switches to two northbound lanes and one southbound lane and heads into Wright Township, becoming a three-lane road with a center turn lane as it passes near wooded residential development and runs through the community of Konns Corners. The road runs through forests with some commercial development, crossing into Fairview Township. The route heads near homes and businesses in the community of Fairview Heights, becoming North Mountain Boulevard and widening to five lanes. PA 309 narrows back to three lanes and heads through the community of Mountain Top, curving to the northwest and coming to an intersection with the northern terminus of PA 437 in the community of Fairview. The road runs through forested areas as it traverses Penobscot Mountain, narrowing to two lanes before turning into a four-lane divided highway. The route curves north and enters Hanover Township, with the median widening as it continues to wind north across the mountain. The median narrows and PA 309 continues northwest, passing southwest of a section of the Pinchot State Forest.