This information is abreviated for people trying to reach the north end of the trail from the west side (Rainy Pass, Mazama, Harts Pass).
If you are flying to Washington, Seattle-Tacoma airport is the best arrival point for 90% of the trailheads in WA. Portland airport is best if you want to enter the trail south of Williams Mine (Trout Lake, Bridge of the Gods, Cascade Locks)
There is no way to complete the route to PCT Section L using only public transit. You will need private transportation for the last leg of the route. To my knowledge taxi, Uber, or Lyft are not options. See the bottom of this page for instructions on requesting a ride from another hiker.
Arriving at SeaTac
Walking to the Sound Transit Light Link Rail Station at SeaTac
From the baggage claim area, go up one level to the ticketing counters. Walk N/NE to the last skybridge over the road. Take that skybridge over the road to the parking garage. Stay on that same level of the parking garage as you walk NE to the far corner of the parking garage. The level you should be on is the only level of the parking garage with windows on the north side, and a wide light-green stripe on the floor. When you reach the NE corner of the parking garage you will see the skybridge to the Light Rail station.
Take Line 1 northbound
If you are staying the night in Seattle
then you can decide which Line 1 stop is best for you.
Continuing north from Seattle
If you are connecting with the Greyhound bus north
(Once daily 11:15 AM) then get off at the Stadium Station.
Walk just a few feet north to S. Royal Brougham Way.
Turn right (east) and walk 1/2 block to the Greyhound Bus Station on 6th avenue S.
Greyhound
If you are connecting with the AmTrak train north
(Amtrak Cascades route, Twice daily 8:30 AM or 6:00 PM) then get off at the International District/Chinatown Station (an underground station).
Take the escalators to the surface. Walk south through the plaza to S Weller Street.
Turn Right (west) and go 1/2 block to the Weller St pedestrian bridge.
At the far end of the pedestrian bridge you will go down the stairs to the street level and turn right (north).
The train station is right in front of you on the right side of the street.
AmTrak
Note, both the bus and the train advertise WiFi on board.
Mount Vernon Park & Ride
Depart either the train or the bus at the Mount Vernon Park & Ride on E. Kincaid Street, right next to Interstate 5 (exit 226). If you need a hotel in Mt Vernon, there are four inexpensive hotels one highway exit north of the bus stop, or about 1.5 miles walk north from the bus stop.
Mt Vernon to Mazama
From there you can either continue on to Concrete, WA by bus (still 90 miles from Mazama, WA), or you can arrange for a ride from a Trail Angel.
Requesting a ride the rest of the way
You can request a ride on the Facebook group PCT Washington Trail Angels. It's best to wait until about 1 week prior to ask for a ride. Otherwise, people are hesitant to commit.
Be sure the highway is open
State Route 20 closes when the snow begins to stick to the road. The earliest that has happened was October 31st 1994, the latest that has ever happened was December 30th 1974.
SR 20 will typically open before May 1st, well before the trail begins to emerge from the snow. 2022 was a heavy snow year - it opened May 7th 2022. This millenium the earliest SR 20 has ever opened is March 22nd 2001, and the latest was May 25th 2011. Historical Mountain Pass Open and Closure dates
The bus to Concrete
The closest you can get to Rainy Pass from the west via public transit is Concrete, WA which is still 69 miles from Rainy Pass and has no hotels.
Skagit Transit Route 70X will take you from Mt Vernon Park & Ride to the Concrete Park & Ride located at on N. Superior Ave, Concrete, WA.
Skagit Transit
Coming from Vancouver British Columbia, Canada
The same bus and train route that gets you to Mount Vernon, WA from Seattle, also gets you there from Vancouver, BC.
Coming from Bellingham airport
Bellingham airport is closer to Highway 20, but requires a slightly more complex bus route from there to Burlington or Mt Vernon to connect with trail angel rides.
Route 3 - From the Bellingham airport to the WTA Bellingham Station (E Magnolia St.)
Route 80 From the WTA Bellingham Station to the Chuckanut Park & Ride in Burlington or the Mount Vernon Park & Ride.