 In the original 1928 routing, PA 73 ran between PA 23 near Blue Ball and US 1 (Roosevelt Boulevard) in Philadelphia. The route followed the New Holland Road north through Bowmansville and Knauers to Reading, where it passed through the city along US 222 (Lancaster Avenue), Bingaman Street, Chestnut Street, and US 422 (Perkiomen Avenue). From Reading, PA 73 split from US 422 in Mount Penn and followed Carsonia Avenue and Friedensburg Road to Oley, where it picked up its current routing to Cheltenham Township. Here, PA 73 continued east along Church Road, Township Line Road, and Cottman Avenue to US 1. Upon being designated, PA 73 was paved between south of Reading and Schwenksville and between Skippack and Philadelphia. After the Tacony-Palmyra Bridge was built in 1929, the eastern terminus was moved to its current location on the bridge at the New Jersey state line. It followed Cottman Avenue, US 13 (Frankford Avenue), and US 422 (Levick Street) to the bridge.
