Near the south end of the Yakima River Canyon, which cuts across the Umtanum Ridge, SR 821 crosses into Kittitas County. The two-lane highway generally runs along the bottom of the canyon, to the east of the river and railroad and paralleled to the east by I-82. At its south end, the highway passes downhill from an earlier alignment that was tunneled under a section of the ridge. At Roza Dam, the railroad crosses over to the west side of the river while SR 821 stays uphill from the river, cutting through part of the ridge. The highway continues north, following the cliffs along the meandering river and opposite the railroad and the Wenas Wildlife Area to the west. It passes through of land owned by the Bureau of Land Management, which includes several campgrounds, boat launches, and four recreational areas. The area also has several cattle ranches and farms centered around the Burbank Valley. Midway through the valley, SR 821 passes the Canyon River Ranch, an isolated rest area with shops, restaurants, and cabins that is planned to grow into a resort.