
When first designated, US 309 followed the present corridor of PA 309 to Allentown before heading further east through Slatington, Palmerton, Lehighton, Jim Thorpe, and Nesquehoning and then following present-day PA 309 between Hazleton and Wilkes-Barre. Route 309 ( US 309) was designated to run from US 120 (later renamed US 422) in the Chestnut Hill neighborhood of Philadelphia north to US 11 in Wilkes-Barre. The surface road sections of the route between Philadelphia and the Lehigh Valley follow a turnpike called the Bethlehem Pike that was built in the 1800s. PA 309 heads into Wyoming Valley and passes through the Wilkes-Barre area on a freeway alignment along I-81 and the North Cross Valley Expressway before turning into a surface road again, where it runs through Dallas before reaching its northern terminus. The route continues north into the Coal Region, passing through Tamaqua before it reaches Hazleton.

PA 309 then enters the Lehigh Valley, where it joins Interstate 78 (I-78) on a freeway bypassing Allentown to the south before splitting to the north and running through rural areas as a surface road. In Bucks County, the route has a freeway section bypassing Sellersville before passing through Quakertown as a surface road. PA 309 heads north from Philadelphia and becomes a freeway called the Fort Washington Expressway through suburban areas in Montgomery County, passing through Fort Washington, before becoming a surface road called Bethlehem Pike and running through Montgomeryville. The highway connects Philadelphia and its northern suburbs to Allentown and the Lehigh Valley, and Hazleton and Wilkes-Barre in the Wyoming Valley. The route runs from an interchange between PA 611 and Cheltenham Avenue on the border of Philadelphia and Cheltenham Township north to an intersection with PA 29 in Bowman Creek, a village in Monroe Township in Wyoming County. Pennsylvania Route 309 ( PA 309) is a state highway that runs for 134 miles (216 km) through eastern Pennsylvania. Philadelphia, Montgomery, Bucks, Lehigh, Schuylkill, Carbon, Luzerne, Wyoming I-276 Toll / Penna Turnpike in Fort Washington
