Cal. Gov. Code § 23153
The boundaries of Trinity County are as follows:
Beginning at the northeast corner of Mendocino and southeast corner of Trinity as established and marked by Wm. H. Fauntleroy in 1872, on the summit of the Coast Range at or near the quarter section corner on the east line of Sec. 34 in T. 25 N., R. 10 W., M. D. B. & M.; thence northerly along the summit of said range and the line of Tehama to the northwest corner of Tehama; thence northeasterly and northerly along the summit of the mountain dividing the waters flowing into Sacramento River and the waters flowing into Trinity River on the west line of Shasta and Siskiyou to a point in the southern line of Siskiyou located in Sec. 26, T. 41 N., R. 6 W., M. D. B. & M.; thence southwesterly and westerly along the summit of the mountain dividing the waters flowing into Trinity River from the waters flowing into the Scott and Salmon Rivers to the intersection of the east line of Humboldt on what is known as Salmon Summit, being the northwest corner of Trinity near the corner to Secs. 4, 5, 8, and 9, T. 9 N., R. 7 E., H. B. & M.; thence southwesterly and southerly by the eastern line of Humboldt to the southwest corner of Trinity as surveyed and marked by Wm. H. Fauntleroy in August, 1872, the same being in the SE. 1/4 of Sec. 31, T. 5 S., R. 6 E., H. B. & M.; thence east along the line between Trinity and Mendocino, as surveyed and marked by Wm. H. Fauntleroy in 1872 to the point of beginning.
Ca. Gov. Code § 23153