At the south end of Clarkston near Swallows Park, SR 129 intersects Fleshman Way in a dogbone interchange on the western approach to the Southway Bridge. Fleshman Way passes over SR 129 and continues west towards former SR 128 and east across the Snake River to Lewiston, Idaho. The highway continues north from the interchange and enters Clarkston city limits, becoming 5th Street before cutting across to 6th Street. The street passes through downtown Clarkston and splits from 6th Street to follow Diagonal Street as it runs four blocks northeast towards US 12. SR 129 terminates a half-block from the Idaho state line at the intersection with US 12, which provides eastbound connections to downtown Lewiston on Bridge Street; the remaining two-block section of 6th Street is signed as SR 129 Spur and provides connections to westbound US 12.