We actually had at least one incident of "underground railroad" in the early history of Puget Sound. Washington Territory was considered "free soil", but if you already owned slaves when you arrived here, it was OK to keep them.

The original Territorial Surveyor moved from Maryland to Olympia, Washington and brought a young slave, Charles Mitchell, along.

The story of how the incident evolved, and the role played by a steam sidewheeler:

http://digital.turn-page.com/i/269242/3