State Road No. 10 Chelan-Okanogan Highway began at Jct. State Road No. 7 North Central Highway in Quincy and headed westerly, then northwesterly to East Wenatchee. At East Wenatchee, the Chelan-Okanogan Highway joined State Road No. 2 Sunset Highway. The two highways headed northerly up the east side of the Columbia River to Orondo. At Orondo, the two highways split, with the Sunset Highway turning right and heading east to Spokane and the Chelan-Okanogan Highway continuing straight ahead. At Beebe, the Chelan-Okanogan Highway crossed the Columbia River to Chelan Falls. From Chelan Falls, the highway headed northerly to Pateros, then easterly to Brewster, then northerly up the Okanogan Valley to Okanogan, Omak, Tonasket, and Oroville, ending at the Canadian border.
In 1926, State Road No. 10 from East Wenatchee to the Canadian border became part of US 97. Although State Road No. 10/US 97 existed on paper between Orondo and Hugo (a few miles north of Chelan Falls) parts of this route had not yet been built. The actual travelled roadway, shown on maps as Temporary State Road No. 10/ Temporary US 97, followed the west side of the Columbia River from the Wenatchee area via Entiat and Chelan to Hugo. When the State Road designations in state law were replaced by the Primary State Highway designations in 1937, State Road No. 10 became Primary State Highway (PSH) 10. The route of PSH 10 and US 97 from the Wenatchee area to Hugo followed the west side of the Columbia River. Former State Road No. 10 from Orondo to Hugo became Secondary State Highway (SSH) 10D
Brewster-Coulee City Branch
The Brewster-Coulee City Branch of State Road No. 10 Chelan-Okanogan Highway was added to the state highway system in 1931. This branch began at a junction with the State Road No. 3 trunk in Brewster and headed south across a bridge over the Columbia River, then southeasterly to Bridgeport, then southerly to Mansfield, then east to Sims Corner, then southerly, ending at Jct. State Road No. 2 Sunset Highway a few miles wes of Coulee City. This route was redesignated as the Brewster-Coulee City branch of Primary State Highway 10 in 1937.
Primary State Hwys Secondary State Hwys
State Roads 1923-37