In the 1950s, US 309 was shifted to a new alignment farther west between Allentown and Hazleton, and PA 29 was shifted to use the road between Lehigh Gap and Weissport along with PA 45. In 1955, US 22 was moved to the Lehigh Valley Thruway, and PA 45 was extended east along Northampton Street through downtown Easton to the Northampton Street Bridge over the Delaware River while the former alignment of US 22 along Prospect Avenue, Pearl Street, and Bushkill Street became unnumbered. In 1961, PA 29/PA 45 was upgraded to a divided highway between Weissport and Lehigh Gap, with the portion south of Bowmanstown constructed as a freeway. The freeway between Palmerton and Bowmanstown was built on a new alignment to the west, the routes previously followed State Road, Mauch Chunk Road, and White Street between the two boroughs. On May 9, 1966, PA 248 was designated to run from US 209 in Weissport east to US 611 (now PA 611) in Easton along its current alignment, replacing the PA 45 designation between Weissport and Easton along with PA 29 between Weissport and Lehigh Gap.