SR 129 enters Asotin near the county fairgrounds and meanders around a residential neighborhood before turning north onto Washington Street at the east end of downtown. The highway then turns west onto 1st Street, passing north of the downtown strip and the county courthouse. 1st Street remains parallel to the Snake River, accessed via Chief Looking Glass Park on the city's waterfront, and SR 129 continues northwest out of the city along the river as Riverside Drive. The highway continues northeast along the river bank and a parallel bicycle path towards Clarkston, passing downhill from residential areas on the west and the Lewiston–Nez Perce County Airport to the east in Idaho.