Helena Montana to Calgary CA to Vancouver to Seattle WA

FYI, Anacortes isn't on the Olympic Peninsula, but on Fidalgo Island. That's the only one of the San Juan Islands you can drive to and is about 30 miles west of I-5. If you do visit, you needn't double back to I-5. You can head over the Deception Pass bridge and drive to the south end of Whidbey Island and take your rig on a ferry to Mukilteo. One of the routes from there to I-5 goes right by the Boeing 747/767/777 factory, where they do guided public tours.