Idaho Code § 31-143
Teton county is described as follows: beginning at a point on the northern boundary line of Bonneville county, the said point being two (2) miles east of the range line, which, when surveyed, will be between ranges forty-two (42) and forty-three (43) east;
Southern boundary. Thence easterly and southerly on the northern boundary line of Bonneville county as now established, to a point where said boundary line intersects the boundary line dividing the states of Idaho and Wyoming;
Eastern boundary. Thence north along the boundary line between the states of Idaho and Wyoming, to a point where said dividing line intersects Bitch creek;
Northern boundary. Thence westerly and down the center of said Bitch creek, to a point where said Bitch creek intersects and runs into the main channel of the Teton river, and to the center of said main channel; thence down the said main channel of the said Teton river, to a point where the same intersects the section line between sections sixteen (16) and seventeen (17), township seven (7) north, range forty-three (43) east;
Western boundary. Thence south along said line to the place of beginning.
County seat-Driggs.
Idaho Code § 31-143