California Code, Government Code - GOV § 23117

The boundaries of Lake County are as follows:

Beginning at the monument on top of Mount Hull, established by T. P. Smythe and R. P. Hammond and party on October 20, 1885, and approved by H. J. Willey, Surveyor-General of the State of California, on December 23, 1885; thence due north to the half section line running east and west through Sec. 2, T. 19 N., R. 10 W., M.D.B. & M.; thence east along said half section line through Secs. 2 and 1 of said township, range, base and meridian, and then through Sec. 5 to the southeast corner of the NE 1/4 of said Sec. 5, T. 19 N., R. 9 W., M.D.B. & M.; thence north along the line between and dividing Secs. 4 and 5 of said township, range, base and meridian, and continuing north along the line between and dividing Secs. 32 and 33, 28 and 29, 20 and 21, to the common section corner of Secs. 16, 17, 20, and 21, T. 20 N., R. 9 W., said section corner being on the eastern boundary of Mendocino and being also the common corner of Lake and Glenn; thence east between Secs. 16, 21, 15, 22, 14, 23, 13, 24, of T. 20 N., R. 9 W., M.D.B. & M., and Secs. 18, 19, 17, 20, 16, 21, 15, 22, T. 20 N., R. 8 W., M.D.B. & M., to corner of Secs. 14, 15, 22, 23, T. 20 N., R. 8 W., M.D.B. & M.;

Thence south between Secs. 22, 23, 26, 27, 34, 35, T. 20 N., R. 8 W., M.D.B. & M., and Secs. 2, 3, 10, 11, 14, 15, 22, 23, 26, 27, 34, 35, T. 19 N., R. 8 W., M.D.B. & M., and Secs. 2, 3, 10, 11, 14, 15, 22, 23, 26, 27, to one-quarter section corner on the section line dividing Secs. 26 and 27, T. 18 N., R. 8 W., M.D.B. & M.; said point being on the boundary line between Glenn and Colusa; thence running westerly along the half section line and one and one-half miles north of the line dividing T. 17 and 18, M.D.B. & M., to the northwest corner of the southwest one-quarter of Sec. 30, T. 18 N., R. 8 W., M.D.B. & M., said corner being also the northwest corner of Colusa;

Thence southerly on the western line of Colusa and Yolo to the point on said Yolo line, where said line is intersected by the boundary line between Napa and Lake; thence southwesterly in a straight line to a large pile of rocks on the southeasterly side of the county road, at the lower and most easterly end of Hunting Valley; thence down Hunting Creek to its junction with Jericho Creek in Jericho Valley; thence down Jericho Creek to its junction with Putah Creek; thence southwesterly in a direct line to the Buttes Canon road at a point near the northwest corner of Sec. 19, T. 10 N., R. 5 W., said point being on the line between Lake and Napa; thence westerly on said line to the summit of Mount St. Helena; thence northwesterly along the summit of the Mayacmas Range, being the dividing ridge between the waters flowing into Russian River and those flowing into Clear Lake, to the southeast corner of Mendocino and the northeast corner of Sonoma; thence northerly along the eastern line of Mendocino to the place of beginning.