There are two ways to ride to Port Townsend from Seattle. This route begins with a to the ferry crossing at Mukilteo . You can ride to Port Townsend in a single day by doing the Seattle/Bainbridge ride.

The ride to Mukilteo is a dedicated bike path most of the way and follows the lakeshore for the first half. I will start the mapping from Amtrak’s King street station. Find your way to 2nd Avenue, just a couple blocks from the station, and follow the dedicated bike lane north. Note the bike lane is bidirectional even though you are riding opposite the direction of traffic. There are also dedicated bike signals to protect you from turning traffic.

In one mile, turn right onto Blanchard and then left onto 7th, which becomes Dexter. Once you cross Mercer avenue, turn right onto Roy to connect to the Cheshiahud Westlake bike trail heading north. This will follow lake Union until it curves and crosses the Fremont bridge. As the path turns just before reaching the bridge, be sure to follow the signs for Fremont (left at the split) so that you don’t end up on the South Ship canal trail.

After crossing the Fremont bridge, turn right on N. 24th street and ride a quarter mile before seeing signs for the Burke Gilman trail on your right. Continue on the trail in the same direction (east).

Ride the Burke Gilman bike trail for about 11 miles before turning left onto Ballinger way. From here, there are multiple routes to get to the Mukilteo ferry landing:

You can take Ballinger and turn right on 40th (which becomes 37th and then Cedar way). Turn left on 236th to Ballinger Lake and connect with the Interurban trail to the intersection with the 405 freeway.
You can shortcut to Interurban path by taking Ballinger to 40th, then following that until it becomes Cedar/44th before bringing you to the Interurban path.
You can take Google’s direct route up 30th since it’s the only bike recommended option
I prefer the the first option because it maximizes riding along a dedicated bike path despite being a less direct route.

At I405, leave the Interurban trail and follow Alderwood Mall parkway north to 148th street. Turn left and then right on Admiralty way, then left on Lincoln which will bring you to the Mukilteo speedway. As its name suggests, it is a busy highway but it does have a dedicated bike lane. Continue right (north) on the Speedway.

Follow the signs for the Mukilteo ferry. You can either spend the night here (I booked a bed and breakfast) or continue on to Clinton if you have the energy. If you go over to the island this day, I recommend staying in Langley as it’s an adorable little village.

The next day, you will ride to Port Townsend.