CA Elec Code § 21500 (2021)
2021 California Code|Elections Code - ELEC|DIVISION 21 - STATE AND LOCAL REAPPORTIONMENT|CHAPTER 6 - Supervisorial Districts|Section 21500.

21500.  (a) Following a county’s decision to elect its board using district-based elections, or following each federal decennial census for a county whose board is already elected using district-based elections, the board shall, by ordinance or resolution, adopt boundaries for all of the supervisorial districts of the county so that the supervisorial districts shall be substantially equal in population as required by the United States Constitution.(1) Population equality shall be based on the total population of residents of the county as determined by the most recent federal decennial census for which the redistricting data described in Public Law 94-171 are available.(2) Notwithstanding paragraph (1), an incarcerated person, as that term is used in Section 21003, shall not be counted towards a county’s population, except for an incarcerated person whose last known place of residence may be assigned to a census block in the county, if information about the last known place of residence for incarcerated persons is included in the computerized database for redistricting that is developed in accordance with subdivision (b) of Section 8253 of the Government Code, and that database is made publicly available.(b) The board shall adopt supervisorial district boundaries that comply with the United States Constitution, the California Constitution, and the federal Voting Rights Act of 1965 (52 U.S.C. Sec. 10301 et seq.).(c) The board shall adopt supervisorial district boundaries using the following criteria as set forth in the following order of priority:(1) To the extent practicable, supervisorial districts shall be geographically contiguous. Areas that meet only at the points of adjoining corners are not contiguous. Areas that are separated by water and not connected by a bridge, tunnel, or regular ferry service are not contiguous.(2) To the extent practicable, the geographic integrity of any local neighborhood or local community of interest shall be respected in a manner that minimizes its division. A “community of interest” is a population that shares common social or economic interests that should be included within a single supervisorial district for purposes of its effective and fair representation. Communities of interest do not include relationships with political parties, incumbents, or political candidates.(3) To the extent practicable, the geographic integrity of a city or census designated place shall be respected in a manner that minimizes its division.(4) Supervisorial district boundaries should be easily identifiable and understandable by residents. To the extent practicable, supervisorial districts shall be bounded by natural and artificial barriers, by streets, or by the boundaries of the county.(5) To the extent practicable, and where it does not conflict with the preceding criteria in this subdivision, supervisorial districts shall be drawn to encourage geographical compactness in a manner that nearby areas of population are not bypassed in favor of more distant populations.(d) The board shall not adopt supervisorial district boundaries for the purpose of favoring or discriminating against a political party.(e) For purposes of this chapter, “adopt” or “adoption” in regard to supervisorial district boundaries means the passage of an ordinance or resolution specifying those boundaries.(Amended by Stats. 2021, Ch. 320, Sec. 2. (SB 594) Effective September 27, 2021.)