Advise on Travel on I-5 from California to Vancouver BC in late December-January

[nexus73]

I am not sure if that was Mt Shasta or not.

Yes, it was. Shasta has snow year-round and on a clear day, can be seen as far south as Sacramento. The surrounding area is very flat so it has a huge amount of prominence. Likewise, you can see it from as far north as Crater Lake in Oregon. It's also easily viewed from the Lassen summit.

US-97 about 10 miles northeast of Weed has a good viewing platform you can pull into. It's almost directly north of the mountain and you get one of the best unobstructed views. Also has some signs explaining the history of the mountain, and how the current mountain was formed much more recently than I would have expected (it's a young mountain similar to Mt. St. Helens).

The original alignment of 101 between Gold Beach and Brookings had a high point from which Mt. Shasta could be seen on a clear day. 

[pderocco]

The original alignment of 101 between Gold Beach and Brookings had a high point from which Mt. Shasta could be seen on a clear day.

That (Carpenterville Rd) looks like an interesting road to drive, but in Google Earth I don't see any point along it that's anywhere near high enough to see over the intervening mountains all the way to Shasta. You'd have to be at around 4000ft, and the highest that goes is 1700ft. Perhaps there's a side road off it somewhere that goes up a mountain?

[nexus73]

The original alignment of 101 between Gold Beach and Brookings had a high point from which Mt. Shasta could be seen on a clear day.

That (Carpenterville Rd) looks like an interesting road to drive, but in Google Earth I don't see any point along it that's anywhere near high enough to see over the intervening mountains all the way to Shasta. You'd have to be at around 4000ft, and the highest that goes is 1700ft. Perhaps there's a side road off it somewhere that goes up a mountain?

All I know is what was told me by others when I was quite young.  YMMV when it comes to visuals.

[Quillz]

The original alignment of 101 between Gold Beach and Brookings had a high point from which Mt. Shasta could be seen on a clear day.

That (Carpenterville Rd) looks like an interesting road to drive, but in Google Earth I don't see any point along it that's anywhere near high enough to see over the intervening mountains all the way to Shasta. You'd have to be at around 4000ft, and the highest that goes is 1700ft. Perhaps there's a side road off it somewhere that goes up a mountain?

That's because I'm pretty sure you can't see Shasta from the 101. The Klamath Range reaches up to 9,000 feet and there are too many mountains in the way to see over it. As nexus noted, he's repeating hearsay, so it's far more likely whoever told him that was confusing another mountain for Shasta. It's possible something like Mt. Ashland could be seen from the 101, as it's a fair bit more inland than Shasta.

The reason why Shasta is so prominent from other directions is because how flat the surrounding area is. From the north, you can see it from Crater Lake. From the south, you can see it from Sacramento. From the east, it's easily visible from Lassen or even as far east as Alturas. But the west has the Coast Ranges and they block the visibility.