Primary State Highway 10-Okanogan Highway

PSH 10 (Trunk)

PSH 10 began at Jct PSH 7 in Quincy and headed NW via Rock Island to Jct PSH 2 in East Wenatchee. From East Wenatchee to the Azwell area north of Chelan, the state intended for several years to run PSH 10 along the east side of the Columbia River to a bridge from Beebe to Chelan Falls. Maps from the 1920s and early 30s show this route as State Highway 10 and the route via Entiat and Chelan as Temp State Highway 10. By the late 1930s, PSH 10 from Orondo to Azwell had been redesignated as SSH 10D. US 97 was finally moved to the long planned eastern PSH 10 route in 1988. The route that became PSH 10 in the later 1930s joined PSH 2 at East Wenatchee, crossed the Columbia River to Wenatchee and the Wenatchee River to Olds Station. At Olds Station, PSH 10 left PSH 2 and headed up the west side of the Columbia River via entiat and Chelan to Azwell and Pateros. PSH 10 curved east along the river a to Brewster and Jct PSH 10 BB. From Brewster, PSH 10 headed NNE to Okanogan, Omak, Tonasket, Oroville, and the Canadian Border, where PSH 10 ended. In the 1950s, after Chief Joseph Dam was completed, PSH 10 was routed east across the Okanogan River to Jct PSH 10 BC near Fort Okanogan State Park, then north along the east side of the Okanogan River to the Okanogan-Omak area.

Today, PSH 10 from Quincy to East Wenatchee is SR 28; from Olds Station to Azwell, Alt US 97; from Azwell to the Canadian Border, US 97.

PSH 10BC originally started at Jct PSH 10 at Brewster and headed south across a bridge over the Columbia River, then SE via Bridgeport to Jct PSH 2 a few miles west of Coulee City. In 1951, the junction of PSH 10BC with PSH 10 was moved to the vicinity of Fort Okanogan State Park, a few miles east of Brewster. The new route of PSH 10BC headed SE, crossing the Columbia River a short distance downstream from Chief Joseph Dam. South of the bridge, the new alignment rejoined the previous alignment at Bridgeport. Since 1964, PSH 10BC has been posted as SR 17.

Before 1951, PSH 10BB had been part of PSH 10BC. In 1951, the portion of PSH 10BC from PSH 10 to Bridgeport was rerouted as described above. Former PSH 10BC from Brewster to Bridgeport was redesignated as PSH 10BB. Since 1964, this highway has been signed as SR 173.