Washington State Route 31

The shield of PSH 6 (1937–1964)

In 1923, a system of roads to connect cities throughout Washington was established.[6] One of the roads, State Road 6, followed a route from Spokane to the Canada–US border.[6] The road was named the Pend O'Reille Highway,[6] a name that would identify the route until 1964.[7] The state road system was later expanded into a new system in 1937.[7]

During the creation of the Primary and Secondary Highways in 1937, the road that was State Road 6 became Primary State Highway 6 (PSH 6).[7] PSH 6 ran from U.S. Route 10 (US 10) and US 195 (future US 2), north to the Canada–US border; the route was co-signed as US 195 from Spokane to Newport.[7] US 2 was signed over PSH 6 from Spokane to Newport in 1948 and the route became SR 31 from Newport to the Canada–US border during the 1964 highway renumbering. During the renumbering, WSDOT replaced the previous system of Primary and Secondary Highways with a new system called State Routes, which is still in use today.[8][9]

SR 31's route from 1964 until 1973

SR 31's previous route ran a total of 73.31 miles (117.98 km) from Newport northwest to Tiger and north to the Canada–US border at BC 6.[10] The route started in Newport at the intersection of W. Walnut Street (SR 31 northbound and US 2 eastbound) and N. Union Avenue (US 2 westbound). Next, the highway went northwest and left Newport to parallel the Pend Oreille River for the rest of its route.[11] The road would also join the Pend Oreille Valley Railroad north to the current southern terminus.[4] SR 31 turned west and passed Lake Newport State Park, located on the shores of the river,[12] before curving northwest and entering the community of Dilkena. From Dilkena, the road goes north to pass SR 311's northern terminus in Usk and pass the towns of Cusick, Locke and Jared. The highway turned east at Jared and back northwest at Ruby. After Blue Slide and Lost Creek, SR 31 would continue north out of Tiger, which was the eastern terminus of SR 294.[11] SR 31 from Newport to Tiger later became SR 20 after it was extended on SR 294 and SR 31 in 1973.

Former SR 311's shield that identifies the route.

From 1964 until 1973, SR 31 had an auxiliary route called State Route 311. The highway ran from US 2 west of Newport, north 15.24 miles (24.53 km) to SR 31 in Usk.[10] The road was entirely located within Pend Oreille County; the southern terminus was located east of Pend Oreille State Park on US 2 and west of Diamond Lake and the community of the same name.[13][14] SR 311 advanced north past Sacheen Lake and Davis Lake to the northern terminus,[15] which was 2.39 miles (3.85 km) south of Cusick.[10] SR 311 was established as SSH 6B in 1937 during the creation of the primary and secondary highway system.[7] In the 1964 renumbering, SR 311 was created over SSH 6B.[8][9] When SR 20 was extended over SR 294 and SR 31, SR 311 became SR 211, which it is still currently designated as.