Wash. Rev. Code § 36.04.240
Okanogan county shall consist of the territory bounded as follows, to wit: Beginning at the intersection of the forty-ninth parallel with the range line between ranges thirty-one and thirty-two east, and from thence running in a southerly direction on said range line to the intersection of the said range line with the Columbia river, and thence down the river to the seventh standard parallel north; thence west along the seventh standard parallel north to the watershed between the waters flowing northerly and easterly into the Methow river and the waters flowing southerly and westerly into Lake Chelan; thence in a general northwesterly direction along the summit of the main divide between the waters flowing northerly and easterly into the Methow river and the waters flowing westerly and southerly into Lake Chelan and its tributaries; following the course of the center of the summit of the watershed dividing said respective waters to the point where the same intersects the east boundary of Skagit county and the summit of the Cascade mountains; thence northerly with said summit to the forty-ninth parallel, and thence on the said parallel to the place of beginning.
RCW 36.04.240