Since my first thread about public transit from SD-LA seemed to generate so much interest, here's another public bus adventure which I've done a few times. There's a one mile gap which must be walked since no public transit crosses the border.

If you love nature, it's a great ride. You start out on a ferry with expansive views of the Puget Sound Area, then through Whidbey Island, which is stunning to say the least (look up pictures of Deception Pass). Mt. Vernon to Bellingham is unremarkable since it uses I-5, but the city of Bellingham is a really great place to spend a few hours. If you take the non-express route to Blaine, there's plenty to see. Don't forget to keep an eye out for awesome Mt. Baker looming large to the east-south-east.

Port Townsend - Downtown Vancouver
COST: $6.25
TIME: 7 hours and up
DISTANCE: ~130 miles

Itinerary:
1) WSF: Port Townsend - Keystone, $2.60
2) Island Transit #6: Keystone Ferry - Oak Harbor, FREE
3) Island Transit/SKAT #411W: Oak Harbor - Skagit Station, FREE
4) WTA/SKAT #80X: Skagit Station - Bellingham, $0.75
5) WTA #70X: Bellingham - Blaine, $0.75

6) In Blaine, at the last stop (city hall), ask to stay on the bus until the driver returns to Bellingham, and get off at the first stop (it'll save you a few minutes walking). Continue walking towards the highway overpass (500 ft). Before you finish crossing under it, take your first left and you'll see the US customs and immigration post (500 ft). Continue past that 1/4 mile to its Canadian counterpart. You must check in there. Welcome to Canada!

Continue walking on Hwy 99 another 1/4 mile, and take the first exit. Cross the highway using the overpass, and you should see the bus shelter. It's address is 8th Ave & King George Hwy located in White Rock South.

7) Translink #375: White Rock South to White Rock Centre, CAD$2.25*
8) Translink #351: White Rock Centre to Downtown Vancouver, free w/transfer

* The $2.25 fare is only available during off-peak hours.

You can start this adventure in many other cities in Kitsap, Mason, Jefferson and Clallam counties using the appropriate transit agency (Google these for further info).

Downtown Seattle - Downtown Vancouver
COST: $8.10
TIME: 14 hours (due to 5hr forced layover in Bellingham)
DISTANCE: ~141 miles

1) ST Express #510: Downtown Seattle - Everett Amtrak, $2.50
2) SKAT #90X: Everett Amtrak - Skagit Station, $2.00*
3) See steps 4-8 on the Port Townsend-Vancouver itinerary above

* You must use one of the early morning departures since none of the afternoon departures will allow you to make it all the way to Canada in one day

References
Washingon State Ferries (WSF): http://www.wsdot.wa.gov/ferries/
Skagit County Transit (SKAT): http://www.skat.org/
Island Transit (Whidbey Island): http://www.islandtransit.org/
Translink (Vancouver): http://www.translink.bc.ca/
Whatcom Transit Authority (WTA): http://www.ridewta.com/
Sound Transit (ST): http://www.soundtransit.org/

Well done.

By my count, you have to leave downtown Seattle before 7:30 a.m. on the #510 bus, in order to arrive at Everett Station by 8:30, which is the last northbound morning departure.

Well done.

By my count, you have to leave downtown Seattle before 7:30 a.m. on the #510 bus, in order to arrive at Everett Station by 8:30, which is the last northbound morning departure.

Correct. :)

There's a lot of possible scheduling options for these itineraries, but this particular one is inflexible, which makes it worthy to note. Thanks.

Awesome! There may actually be a time this comes in handy!

I started to play around with a similar approach to travel between Seattle and Victoria, BC. I didn't follow it through nearly as carefully as mellowg, but if anyone is interested, my starting posts are in this thread (http://www.flyertalk.com/forum/showthread.php?t=747316). It does cost more because you have to pay for the Coho, so it's not public transit all the way, but the Coho is only $11 for a walk-on passenger.

This is like a work of art. I could see doing this if I wanted a different sort of day. Does it work very well to do the border on foot, in either direction? Do you get extra scrutiny?

This is like a work of art. I could see doing this if I wanted a different sort of day. Does it work very well to do the border on foot, in either direction? Do you get extra scrutiny?

It works very well. I never got more scrutiny than the vehicules. Often, because the line of vehicules is so long, it is much quicker going through the border on foot.

Plus, there´s the Peace Park out there, so it´s literally a walk through the park. ;)