Washington State Route 128

State Route 128 (SR 128) begins at an intersection with U.S. Route 12 (US 12) in Clarkston, a city in Asotin County. The road then crosses the Snake River over the Red Wolf Crossing into Whitman County, where it crosses the Starbuck, WA–Spalding, ID route of the Great Northwest Railroad and intersects the eastern terminus of SR 193.^[3][4] At the SR 193 intersection, the highway turns east and continues to the Idaho state line, where it becomes Idaho State Highway 128 (SH-128);^[5] which continues for another 2.198 miles (3.537 km) before ending at US-12 north of Lewiston, Idaho.^[6][7] SR 128 after the US 12 intersection was used by 5,000 motorists daily in 2007 based on annual average daily traffic (AADT) data collected by the Washington State Department of Transportation.^[8]

The first highway that would later become SR 128 was Secondary State Highway 3K (SSH 3K), which was first designated in 1937.^[9] The road ran from Pomeroy in Garfield County southeast to Peola and later northeast to Clarkston, terminating at Primary State Highway 3 (PSH 3), co-signed with U.S. Route 410 (US 410) at both termini.^[9][10] During the 1964 highway renumbering, SSH 3K became SR 128, which ran 42.19 miles (67.90 km);^[11][12] the current route of the highway was occupied by SR 193, which was Secondary State Highway 3G from 1969 to 1970.

In 1990, the state legislature approved an extension of SR 128 across the Red Wolf Crossing (replacing a section of SR 193) and east to the Idaho state line. The extension was in response to the state of Idaho designating Idaho State Highway 128 on the other side of the border.^[13][14] A year later, SR 128 was truncated from Pomeroy to Clarkston along its current route,^[15] a loss of 42.19 miles (67.90 km) in total.^[12] The transfer was estimated to cost the county government $250,000 for maintenance, due in part to 1 mile (1.6 km) of new pavement required near Peola.^[16]

• Highways of Washington State