Wash. Rev. Code § 36.04.070
Columbia county shall consist of the territory bounded as follows, to wit: Commencing at a point in the middle of the channel of Snake river, where the range line between ranges thirty-six and thirty-seven east of the Willamette Meridian intersects said point; thence south on said range line to the northwest corner of township nine north, range thirty-seven east; thence east on the north boundary line of township nine north, range thirty-seven east, to the northeast corner of said township; thence south on the line between ranges thirty-seven and thirty-eight east of the Willamette Meridian, to the northwest corner of township eight north, range thirty-eight east; thence along the north boundary line of township eight north, range thirty-eight east, to the northeast corner of said township; thence due south to the line dividing the state of Washington from the state of Oregon; thence due east on said dividing line to the range line between ranges forty-one and forty-two east; thence north on said range line to the corner of sections thirteen, eighteen, nineteen and twenty-four, township ten north, ranges forty-one and forty-two east; thence west three miles; thence north three miles; thence west one mile; thence north one mile; thence west one mile; thence north three miles; thence west one mile; thence north to the southwest corner of township twelve north, range forty-one east; thence west on township line six miles; thence north on range line between ranges thirty-nine and forty to a point in the midchannel of Snake river; thence down the midchannel of said river to the place of beginning.
RCW 36.04.070