 In the 1950s, US 309 was moved to a new alignment to the west, and part of PA 29 was designated onto the road between Schnecksville and Lehigh Gap.PA 873 was designated onto this road on May 9, 1966 after PA 29 was split into two segments.PA 873 begins at an intersection with PA 309 in the community of Schnecksville in North Whitehall Township, Lehigh County, which is in the Lehigh Valley.