The route runs through rural areas in northern Lehigh County, intersecting the western terminus of PA 329 in Neffs.

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.

From this intersection, the route heads north on a two-lane undivided road, passing a mix of homes and businesses.

In Slatington, PA 873 becomes Main Street and is lined with residences before reaching the commercial downtown, where the road makes a sharp turn to the east and crosses over the Slate Heritage Trail and Trout Creek.

The route turns north onto Walnut Street and passes more businesses before running past a few homes a short distance to the west of Slatington Airport.

[6] With creation of the U.S. Highway System in 1926, the section of road between Schnecksville and Lehigh Gap was designated as part of US 309, a route that ran from Philadelphia north to Wilkes-Barre.