I stumbled on some CHPWs that I needed to finish documenting the former corridor of US Route 99/Legislative Route Number 3 from Hornbrook north to the Oregon State Line. Rather than starting a new blog I just included the new materials into the existing post regarding OR 273 over Siskiyou Pass. Notably US 99/LRN 3 was moved off Hornbrook Highway during 1949. There is some further details about when US 99 moved off Jefferson Road and when I-5 was finished on the California side:
https://www.gribblenation.org/2020/12/oregon-route-273-early-us-route-99-over.html