Section 23107 Of Article 2. Boundaries Of The Several Counties From California Government Code >> Division 1. >> Title 3. >> Chapter 2. >> Article 2.
23107
. The boundaries of Contra Costa County are as follows:
Beginning in the Bay of San Francisco at the northwest point of
Red Rock, being the common corner of Marin, Contra Costa, and San
Francisco; thence up the Straits and Bay of San Pablo, on the eastern
boundary of Marin, to the point of intersection with a line bearing
south 26 1/2 degrees E., and about six and one-quarter miles distant
from the southwest corner of Napa, forming the common corner of
Marin, Solano, Sonoma, and Contra Costa; thence to the Straits of
Carquinez; thence up said straits and Suisun Bay, to the mouth of the
San Joaquin River; thence up said river, to the confluence of the
west and main channels thereof, as laid down on Gibbe's map; thence
up the said west channel, to a point about 10 miles below Moore and
Rhodes' ranch, at a bend where the said west channel, running
downward, takes a general course north, the point being on the
westerly line of San Joaquin, and forming the northeast corner of
Alameda and southeast corner of Contra Costa; thence westerly on the
northern line of Alameda to the easterly line of San Francisco;
thence due northwest, along said easterly line of San Francisco, four
and one-half miles, more or less, to the place of beginning.