The modern alignment of US 97, from the approach on the west side of Spanish Hollow to the junction with modern SR 14, bypassing Hill and Lancaster's canyon road, was completed in 1962 during the construction of the Sam Hill Memorial Bridge.
At this point, I am not sure when, as the pamphlet below says, the "world famous Maryhill Loops" were bypassed. The best I can find so far is "post-WWII."