Cal. Gov. Code § 23152
The boundaries of Tehama County are as follows:
Beginning at the point of intersection of the Sacramento River with the south line of T. 23 N., M. D. B.; thence west, on said line, being the northern line of Glenn to the summit of the Coast Range, being the southwest corner; thence northerly, on said summit line, to the southwest corner of Shasta; thence easterly, on the southern line of Shasta to the northwest corner of Plumas, being the point of intersection of the southern line of Shasta with the summit line of the dividing ridge between the waters of Mill and Deer Creeks, tributaries of the Sacramento River, and Rice's and Warner's Creeks, tributaries of the north fork of the Feather River, forming the northeast corner of Tehama; thence southerly, along said summit line, to the north point of Butte, it being the point where the northern road from Big Meadows to Butte Meadows, by Dye's house, crosses the said summit line; thence southwesterly, in a direct line, to the head of Rock Creek; thence southwesterly, down Rock Creek, to the south line of T. 24 N., M. D. B.; thence west, on said line, to the Sacramento River; thence along said river to the place of beginning.
Ca. Gov. Code § 23152