I-82 was completed east of the canyon over Manastash Ridge in November 1971, bypassing the congested highway through the Yakima River Canyon. The canyon route had been designated as the state's first scenic byway in 1967, following the enactment of the system, and was provisionally numbered and signed as State Route 821. A lower speed limit of was also set on the highway to discourage use by trucks and encourage scenic touring. In 1973, US 97 was rerouted onto I-82 between Ellensburg and Yakima, while the old alignment through the canyon became SR 821. Until the completion of the Thrall Road interchange in the 1980s, SR 821 continued further north to Tjossem Road, where it turned east and crossed I-82. The encroachment of residential development from the north forced the Bureau of Land Management and The Nature Conservancy to buy additional properties in the canyon for preservation in the 1990s.