From Seattle by ferry:

Take Bainbridge Island ferry then follow Hwy 305 through Poulsbo to Hwy 3.  Turn right on Hwy 3 and go North past the Hood Canal Bridge and then east to Port Gamble.

From Edmonds by ferry

Take the Kingston ferry from Edmonds and then follow Hwy 104 to Port Gamble.

From Tacoma

Take Hwy 16 across the Tacoma Narrows Bridge and follow it North until it intersects with Hwy 3.  Take Hwy 3 North past the Hood Canal Bridge and then east to Port Gamble.