It started at SR 17 in Mesa, then headed west to Ringold, where it ended.

[2] From 1964 until 1970,[3][4] SR 170 began at Ringold Road near the Columbia River southwest of Basin City.

[7] That road would later become a section of Secondary State Highway 11A (SSH 11A) in 1937, which ran from Yakima to Connell.

[8][9] In 1953, SSH 11A was relocated due to the development of the Hanford Site and the Hanford–Mesa route became the Ringold branch.

[10][11] Although the roadway was on a map by 1926, the road wasn't finished until after 1963;[5] one year later in 1964, the highway became SR 170,[4] which was later moved to another route near Warden in 1970.