The highway is a remnant of U.S. Route 10 (US 10) in Kittitas County, traveling southeast along the Yakima River from SR 970 in Teanaway to US 97 northwest of Ellensburg.

[5] SR 10 follows the route of the Roslyn branch of the Northern Pacific Railway, built in the Yakima River valley by the late 1890s.

[12] US 10 was temporarily re-aligned over Blewett Pass in the late 1930s, leaving US 97 alone in the Yakima River valley,[13] until US 10 was moved back to its original route in 1946 after US 2 was extended west from Idaho.

[16][17] I-90 opened between Vantage and Snoqualmie Pass in November 1968 and SR 10 replaced US 10 when the state highways were codified in 1970.

[22] The highway had been in need of major repairs and safety improvements, including guardrails and wider shoulders, which the county stated that they would not be able to afford.