After turning south and back north, the highway starts to curve multiple times until intersecting Sullivan Lake Road and being directed northeast. The road turns north and crosses two streams before curving northwest and then northeast to Lake Lucerene. After passing Lake Lucerene, SR 31 passes Crescent Lake and Boundary Lake before ending at the Canada–US border. SR 31's northern end at the Canada–US border is the easternmost crossing in Washington and is located east of Crawford State Park. In 1923, a system of roads to connect cities throughout Washington was established. One of the roads, State Road 6, followed a route from Spokane to the Canada–US border. The road was named the Pend O'Reille Highway, a name that would identify the route until 1964. The state road system was later expanded into a new system in 1937. During the creation of the Primary and Secondary Highways in 1937, the road that was State Road 6 became (PSH 6). PSH 6 ran from (US 10) and (future ), north to the Canada–US border; the route was co-signed as US 195 from Spokane to Newport. 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. SR 31's previous route ran a total of from Newport northwest to Tiger and north to the Canada–US border at . 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. The road would also join the Pend Oreille Valley Railroad north to the current southern terminus. SR 31 turned west and passed Lake Newport State Park, located on the shores of the river, 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 .