Idaho Code § 31-137
Nez Perce county is described as follows: beginning at the northwest corner of section twenty-two (22), township thirty-eight (38) north, range one (1) west;
Eastern boundary. Thence south to the north boundary line of the Nez Perce Indian reservation; thence easterly along said reservation line to the intersection of the same with the line running south between sections fifteen (15) and sixteen (16), township thirty-seven (37) north, range one (1) west; thence south on the said line between sections fifteen (15) and sixteen (16), to the middle of the channel of Clearwater river; thence up the middle of the channel of said Clearwater river to a point where the same is intersected by the section line between sections five (5) and six (6), township thirty-six (36) north, range one (1) east; thence south on the section line between said sections five (5) and six (6) to the middle of the channel of Little Canyon creek (1911, ch. 24, section 2, p. 50); thence down the center of the channel of Little Canyon creek to a point where the same empties into Big Canyon creek; thence up the center of the channel of Big Canyon creek to a point where the same crosses the township line between townships thirty-four (34) and thirty-five (35) north; thence west on said township line to a point where the same crosses Mission creek; thence up the middle of the channel of Mission creek to a point where the same crosses the township line between townships thirty-three (33) and thirty-four (34) north; thence west on said township line to the northeast corner of section four (4), township thirty-three (33) north, range three (3) west; thence south on section lines to the center of the channel of Salmon river (1911, ch. 37, section 2, pp. 77, 78);
Southern boundary. Thence down the middle of the channel of Salmon river to a point in the middle of the channel of Snake river opposite the junction of Salmon river;
Western boundary. Thence northerly along the boundary line between the state of Idaho and the state of Washington to the point where said boundary line is intersected by the middle line of township thirty-seven (37) north;
Northern boundary. Thence east to a point where the Big Potlatch creek intersects with the said middle line of township thirty-seven (37) north; being at the northwest corner of Section 21, T.37N., R.3W. B.M., which corner is marked by a Brass Cap Monument lying east 1845.18 feet from said corner; thence east 1482.82 feet along the north line of said Section 21 to the centerline of Potlatch river, being the point of beginning of said county line; thence continue northerly along the centerline of said Potlatch river the following courses: N.21°36'07"E. 183.18 feet; thence N.34°16'41"E. 1198.35 feet; thence N.13°03'47"W. 296.08 feet; thence N.33°13'49"E. 576.62 feet; thence N.22°07'05"E. 1097.33 feet; thence N.67°00'39"W. 464.34 feet; thence N.12°45'28"W. 367.96 feet; thence N.21°50'14"E. 385.38 feet; thence N.57°36'12"E. 456.93 feet; thence N.27°52'57"E. 661.93 feet; thence N.15°20'14"E. 272.28 feet; thence N.5°04'43"E. 488.49 feet to a point that is west 983.97 feet and N.5°04'43"E. 80.67 feet from the corner common to Sections 9, 10, 15, and 16, T.37N., R.3W. B.M., being marked by a 5/8" iron pin set in a mound of stone by James W. Grow, R.L.S. #749, and by a Brass Cap Monument set 1136.66 feet west of said Section corner; thence continue along the centerline of Potlatch river N.31°52'33"E. 896.41 feet; thence N.21°02'12"E. 343.00 feet; thence N.10°36'14"E. 654.11 feet; thence N.18°33'57"E. 902.43 feet; thence N.18°47'37"W. 514.74 feet; thence N.33°23'33"E. 1343.54 feet; thence N.11°10'52"E. 528.81 feet; thence N.2°06'09"W. 317.10 feet to a point which is east 662.51 feet and N.2°06'09"W. 8.57 feet from the corner common to Sections 3, 4, 9 and 10, T.37N., R.3W. B.M., which corner is marked by a Brass Cap Monument set 1556.70 feet east of said corner set by James W. Grow, R.L.S. #749; thence continue along the centerline of Potlatch river N.10°27'38"W. 755.37 feet; thence N.15°45'00"E. 732.84 feet; thence N.31°23'33"E. 1307.49 feet; thence N.52°26'42"E. 474.82 feet; thence N.10°47'35"E. 233.84 feet; thence N.2°55'30"W. 1395.50 feet; thence N.30°42'01"E. 840.83 feet; thence N.37°18'55"E. 820.62 feet; thence S.85°46'49'E. 1140.68 feet; thence N.63°14'18"E. 784.25 feet; thence N.65°55'57"E. 647.97 feet; thence N.82°19'22"E. 333.65 feet; thence N.69°39'54"E. 343.03 feet; thence N.54°22'07"E. 56.90 feet; thence N.38°21'12"E. 690.57 feet; thence N.3°38'57"E. 618.32 feet; thence N.30°26'40"E. 397.99 feet; thence N.28°34'42"E. 740.46 feet; thence N.7°36'44"E. 869.85 feet; thence N.44°33'29"E. 950.95 feet to a point on the north line of Section 35, T.38N., R.3W. B.M., being the point of terminus of said county line. Said point being west 2811.24 feet from the northeast corner of said Section 35, which is marked by a Brass Cap Monument set 3091.98 feet west of said corner, being set by James W. Grow, R.L.S. #749.
County seat-Lewiston.
Idaho Code § 31-137