SR 127 begins at an intersection with US 12 in the unincorporated community of Dodge, located between Starbuck and Pomeroy in rural Garfield County.

SR 127 crosses the Snake River on the Elmer Huntley Bridge into Whitman County east of the former Central Ferry State Park.

[8] The present route of SR 127 was added to the Washington state highway system in 1913 as part of the Inland Empire Highway,[9] traveling in a circular arc from Ellensburg through the Yakima Valley and into the Palouse towards the Canadian border in Laurier.

[11][12] The United States Highway System was adopted on November 11, 1926, by the American Association of State Highway Officials (AASHO) and included US 295,[13] traveling northeast from US 410 at Dodge to US 195 in Colfax and crossing the Snake River at Central Ferry.

[16][17] The roadway was re-designated as SR 127 after the new sign route number system was codified into the Revised Code of Washington in 1970,[2] traveling 43.82 miles (70.52 km) from US 12 at Dodge to US 195 in Colfax and crossing the Snake River on the Elmer Huntley Bridge, completed in 1969.