Looking northbound on U.S. Route 97 and State Route 20 after their junction near Okanogan, Washington.
The highway enters Washington at Maryhill, a community on the north side of the Columbia River that is home to a state park and Stonehenge replica. US 97 climbs from the river and briefly turns west on State Route 14 (SR 14) before continuing north over the Columbia Hills. The highway passes Goldendale and Goldendale Observatory State Park before turning northeast to cross the Simcoe Mountains via Satus Pass, located 3,107 feet (947 m) above sea level.
US 97 then traverses part of the Yakama Indian Reservation with shrub–steppe land that lies between the Simcoe Mountains and Toppenish Ridge. After crossing the latter, the highway descends into the Yakima Valley, passing through farmland and vineyards. US 97 then turns northwest at a junction with SR 22 in Toppenish and travels through Wapato before leaving the Yakima Indian Reservation and merging with I-82 and US 12 at Union Gap.
Now part of the freeway, US 97 runs north along the Yakima River through Union Gap and neighboring Yakima, where US 12 splits. The freeway then travels northeast over the Umtanum and Manastash ridges to reach the Kittitas Valley. I-82 ends in Ellensburg at a junction with I-90, which US 97 follows for 4 miles (6 km) before reverting to a two-lane road. The highway continues north into the Wenatchee Mountains (part of the Cascades) in Wenatchee National Forest and crosses Blewett Pass at 4,102 feet (1,250 m) above sea level. US 97 joins US 2 near Peshastin, traveling southeast on a divided highway along the Wenatchee River to the Wenatchee area.
The highway bypasses Wenatchee and crosses the Columbia River on the Richard Odabashian Bridge before turning north onto a two-lane road at a junction with SR 28. US 2 and US 97 travel along the east bank of the Columbia River, opposite US 97 Alternate on the west side, to Orondo, where US 2 turns east. US 97 continues north and east along the river to Chelan Falls, where it crosses the Beebe Bridge and is rejoined by the alternate route near Chelan. The highway follows the west bank of the Columbia River to Brewster, where it turns north to continue along the Okanogan River. US 97 then becomes concurrent with SR 20 for 28 miles (45 km) as they bypass Okanogan and Omak and continue through the Okanogan Highlands. SR 20 turns east at Tonasket while US 97 continues north to the Canadian border near Oroville and Osoyoos, where it terminates and becomes British Columbia Highway 97 (BC 97). BC 97 continues through the British Columbia Interior and terminates at the Yukon border, eventually becoming part of the Alaska Highway.