Idaho Code § 31-113
Boundary county is described as follows: beginning at a point on the state line between the states of Idaho and Washington where the same is intersected by the north line of township sixty-three (63) north, range five (5) west;
Southern boundary. Thence east along the said north line of township sixty-three (63) north, ranges five (5) and four (4) west, to the range line between ranges three (3) and four (4) west; thence south along said range line to the southwest corner of township sixty (60) north, range three (3) west; thence east along said south line of township sixty (60) through ranges three (3), two (2) and one (1) west, and ranges one (1), two (2) and three (3) east, to the state line between the state of Idaho and Montana;
Eastern boundary. Thence north along said state line to the international boundary line between the United States and the Dominion of Canada;
Northern boundary. Thence west along said international boundary to its junction with the state line between the states of Idaho and Washington;
Western boundary. Thence south along said state line to the point of beginning.
County seat-Bonners Ferry.
Idaho Code § 31-113