Secondary State Highway 3K (Washington)

State Route 128
A map of Washington's highway system in the Clarkston area with SR 128 highlighted in red.
Route information
Auxiliary route of US 12
Defined by RCW 47.17.255
Maintained by WSDOT
Length:	2.30 mi (3.70 km)
Existed:	1964 – present
Major junctions
West end:	US 12 in Clarkston
	SR 193 near Clarkston
East end:	SH 128 at Idaho state line near Clarkston
Highway system
State highways in Washington Interstate US State Scenic Former PSH 1964 renumbering Former ← SR 127 SR 129 →

State Route 128 (SR 128) is a Washington state highway located in Asotin and Whitman counties, west of the Idaho state line. The 2.30-mile (3.70 km) long route runs north from U.S. Route 12 (US 12) in Clarkston to cross the Snake River and turn east after intersecting SR 193 to terminate at State Highway 128 (SH 128) on the Idaho state line. The highway was originally created in 1964 on a Pomeroy–Clarkston route, replacing Secondary State Highway 3K (SSH 3K), which had been established in 1937; in 1991, the route was changed to its present form.

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. 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); which continues for another 2.198 miles (3.537 km) before ending at US-12 north of Lewiston, Idaho. SR 128 after the US 12 intersection was used by 5,000 motorists daily in 2007 based on average annual daily traffic (AADT) data collected by the Washington State Department of Transportation.