Idaho Code § 31-139
Owyhee county is described as follows: beginning on the Snake river at the mouth of Owyhee river;
Western boundary. Thence south along the eastern boundary line of the state of Oregon to the northern boundary of the state of Nevada;
Southern boundary. Thence east along the northern boundary of the state of Nevada (1 Ter. Sess. 628) to the thirty-eighth (38th) meridian of longitude west from Washington;
Eastern boundary. Thence north along the said meridian to the south boundary of township 7 south range 12 east. Thence west along the south boundary of township 7 south ranges 12, 11, 10 and 9 east to the southwest corner of township 7 south range 9 east. Thence north along the west boundary of township 7 south range 9 east to the northwest corner of said township. Thence east to the southwest corner of township 6 south range 9 east. Thence north along the west boundary of said township to the Snake river;
Northern boundary. Thence down the channel of the Snake river in a westerly direction to the mouth of the Owyhee river, the place of beginning.
County seat - Murphy.
Idaho Code § 31-139