Wash. Rev. Code § 36.04.340
Thurston county shall consist of the territory bounded as follows, to wit: Commencing at the southeast corner of section thirty-two in township nineteen north, range four west; thence east on the township line to the southeast corner of section thirty-two in township nineteen north, range three west; thence north to the middle of the channel of Totten's Inlet; thence along said channel to the waters of Puget Sound, intersecting the line in the channel of Puget Sound west of the southern portion of Squaxen Reservation; thence following said channel to the mouth of the Nisqually river; thence up midchannel of said river to a point where it strikes the north boundary of Lewis county; thence due west to the northwest corner of section twenty-six, township fifteen north, range four west; thence north to the southeast corner of section thirty-four in township eighteen north, range four west; thence west on the township line to the southeast corner of section thirty-two; thence north on the section line to the place of beginning.
RCW 36.04.340