(last updated 4/12/2023)
If you are familiar with the mileage signs posted at the terminus points of US 6 and US 20, you might point to those and say, "The answer is plain to see: US 20 is 160 miles longer than US 6."
If both of those signs were accurate, then obviously US 20 would be longer. But the fact is, only one of those signs is accurate, whereas the other significantly overstates the true mileage. I first realized that based on measurements I took in 2016, and later refined in 2020. But you may well be wondering, "Why is the author so certain that '3365' is the figure that is wrong, as opposed to whatever number he came up with?" The answer is because in 2021 the source of the misinformation was identified, when I and others obtained a copy of AASHTO's 1989 route log (that is the most recent version they have published). We learned that the figure of "3365 miles" listed therein was never intended to represent the cross-country mileage of US 20. Let me explain.
Pretty amazing coincidence...
Heading west from Portland, US 26 enters the path of totality near Mt. Hood, and remains within the path for about 330 miles, all the way to the Idaho border: