Redistricting Resources

Historical Supervisorial District Maps

Maps from 1970 through to the current map are provided to demonstrate how the County of Santa Clara has shifted overtime. The colors represent city boundaries based on maps developed after the 2010 U.S. Census. Here is a link to a document with the maps outlined below and scanned images with boundary descriptions:


1977 Supervisorial District Map


There was a special census in April 1975, which resulted in a new supervisorial district map being adopted in June 1977. A scanned copy of boundaries from 1970 is included with the document above.



1981 Supervisorial District Map

The next U.S. Census was in 1980, and a new supervisorial district map was adopted in September 1981 with the updated population data. A scanned copy of boundaries is included with the document above.




1991 Supervisorial District Map


Following the 1990 U.S. Census, a new map was adopted in September 1991. A scanned copy of boundaries is included with the document above.




2001 Supervisorial District Map


In September 2001 a new map was adopted based on the 2000 U.S. Census population data. 




2011 Supervisorial District Map

The 2010 U.S. Census population had a total population for the County of Santa Clara at 1,781,731. This resulted in a new map being adopted by the Board of Supervisors on June 21, 2011. This map has the current boundaries. Here is a link to an enlargeable version: Current Supervisorial District Map


2021 Advisory Redistricting Commissioner Cynthia Cooper explains the process of "redlining" and why it is important for people to get involved in the process. 

View Community Drawn Maps

Optional video caption

Mapping Software demonstration

At its most basic level, redistricting is the adjustment of election boundaries to create fairer representation, equalize voting strength, and create equitable distribution of political power. The task is conducted for any state, county, city, or other local government with districted elections. In the United States, this commonly occurs once a decade, after the release of new population numbers from the U.S. Census. Attached below is a manual that goes through many of the elements of the redistricting process, with a focus on local redistricting. As the law and practice of redistricting change, some of the descriptions and definitions of terms may need updating. Please review this as a resource throughout the redistricting process. 

Forum Picture

On Saturday, October 2, 2021 the County's redistricting team and Redistricting Partners presented an overview of the redistricting process and input that has been submitted by the community. The Community Redistricting Forum was an opportunity for people to hear about the work of the 2021 Advisory Redistricting Commission and to learn about opportunities to become involved in the redistricting process. Please review the attached presentation to learn more. If you could not make the forum, but would like to submit information on your community for consideration, please fill out a Community of Interest Form, or draw a map documenting your neighborhood or community at

Frequently Asked Questions

QUESTION: What timeframe applies to the campaign contribution requirements that commissioners and applicants "may not endorse, work for, volunteer for, or make a campaign contribution to, a candidate for an elective office of the County?" 

ANSWER: A person would be disqualified from applying to and serving on the Commission if they have already made a contribution, or during their service on the Commission make a contribution, to any person who has already identified themselves as a candidate for an elective office of the County for the 2022 or 2024 cycle  (i.e. has already formed a campaign committee for a 2022 or 2024 election for Supervisor, District Attorney, Sheriff, or Assessor). Once the Commission has completed its work and the Board of Supervisors has adopted the new supervisorial district boundaries, there are no continuing requirements to refrain from endorsing, working for, volunteering for, or making campaign contributions to such candidates. The requirement does not extend to candidates for local, state, or federal officers that are not County officers. 

QUESTION: Will the Advisory Redistricting Commission meetings occur virtually or in person? 

ANSWER: Currently the County is planning to convene virtual meetings. However, the County's ability to convene virtual Brown Act meetings was granted during the COVID-19 State of Emergency as an executive order from the governor. The state of emergency may be rescinded by the state of California and meetings may need to occur in person. There is some legislation pending that may provide for virtual participation, which the County is monitoring closely. 

Screen Shot of Redistricting Commissioners Meeting Over Zoom


QUESTION: I am currently serving as a commissioner on a County commission. Do I need to resign my seat to be considered eligible to be appointed as an Advisory Redistricting Commissioner? 

ANSWER: Yes, applications will be reviewed on June 1st and to be eligible, you will need to resign from your current appointment. 


QUESTION: I don’t have the time to serve as a commissioner. How else can I be involved in redistricting? 

ANSWER: During the redistricting process, community members will have many opportunities to participate including: 

• Apply to be a member of the 2021 Advisory Redistricting Commission 

• Attend and speak at the 2021 Advisory Redistricting Commission meetings 

• Submit maps electronically throughout the process for the district you want or the district map you prefer. 

As new opportunities to participate become available, they will be posted on the County’s redistricting website:


QUESTION: When is the deadline to apply to be a 2021 Advisory Redistricting Commissioner? 

ANSWER: Applications are posted on the County’s website and can be complete online through Docusign. Applications are due on Tuesday, June 1, 2021 at 9:00 am. 


QUESTION: When will the 2021 Advisory Redistricting Commission meet? 

ANSWER: Meetings of the 2021 Advisory Redistricting Commission will occur every other Wednesday from 6:30 pm to 8:30 pm from July through September. From October through November meetings will occur weekly on Wednesdays from 6:30 pm to 8:30 pm. 


QUESTION: Why is redistricting important? 

ANSWER: Every 10 years, the County redraws district boundaries, taking into account population changes reflected in the Census. Redistricting is based on the idea of fair representation and determines which neighborhoods and communities are grouped together into a supervisorial district for purposes of electing a Board of Supervisor member. This will influence how effectively a community is represented in county government.  

The County is encouraging applicants who reflect the diverse composition of our County. Robust community engagement will ensure supervisorial district boundaries are redrawn to best reflect and serve our community. The 15-member commission (3 from each supervisorial district) will hold public hearings and mapping sessions, collect community input, and recommend to the Board of Supervisors an updated placement of the supervisorial district boundaries based on the 2020 census data. The district boundaries must be in place before the next election cycle, so that candidates and voters know which district they reside in. 


QUESTION: How can I learn more about redistricting? 

ANSWER: To learn more visit the County’s website, read the County’s press release, or email the redistricting team at [email protected]

If you are interested in learning more about redistricting, you can visit these additional resources: 

Redistricting Glossary

Accelerations – In an election area where there are four-year terms and elections every two years, a redistricting will result in a situation where a voter just recently elected a representative, then a redistricting happens, their district changes, and they get to again elect a representative just two years later. Technically, in this situation, they have two representatives – the one they elected before the redistricting, and the one they just voted for. Their opportunity to vote has been accelerated by two years. For the opposite, see Deferrals.

American Community Survey - Ongoing statistical survey by the U.S. Census Bureau, sent to approximately 250,000 addresses monthly (or 3 million per year). The ACS regularly gathers information previously contained only on the long form of the decennial census. Data is reported at the block-group or census tract level.

Apportionment - Following each census, the 435 seats in the U.S.  House of Representatives are apportioned to each state based on state population. The larger the state population, the more congressional representatives the state will be apportioned. Apportionment, unlike redistricting, does not involve map drawing.

At-large election system - An at-large election system is one in which all voters can vote for all candidates running for open seats in the jurisdiction. In an at-large election system, candidates run in an entire jurisdiction rather than from districts or wards within the area. For example, a city with three open city council positions where all candidates for the three seats run against each other and the top three vote-getters citywide are elected is an at-large election system.

Bailout – When an agency under Section 5 successfully appeals to the U.S. Department of Justice to be removed from the group of states and counties that are required to receive preclearance for election changes, including redistricting.

Bloc Voting - A behavior of communities in which their voting patterns move as a unit, usually due to race, and their patterns follow their group identity more than traditional other characteristics, like partisanship, age, or left-handedness.

Bullet Voting - a method of voting in a race where the voter can vote for multiple candidates, but supporters agree to only vote for their one most supported candidate, denying other candidates the remaining extra votes, and giving their preferred candidate a mathematical advantage.  Can be used to as a method to strengthen minority voting power.

California Voting Rights Act – A state law prohibiting the use of at-large districts in any agency with racially polarized voting.

Census - The United States Census is a population enumeration conducted every 10 years, the results of which are used to allocate Congressional seats, electoral votes and government program funding. As part of the census, detailed demographic information is collected and aggregated to a number of geographical levels.

Census block - The smallest level of census geography used by the Census Bureau to collect census data. Census blocks are formed by streets, roads, bodies of water, other physical features and legal boundaries shown on Census Bureau maps. Redistricting is based on census block-level data.

Census block group - A collection of census blocks sometimes used for data estimates from the ACS that are not as reliable at the block level.

Census tract - A level of census geography larger than a census block or census block group that sometimes corresponds to neighborhood boundaries and is composed of census blocks.

Coalition District – See Majority Minority Coalition District

Cohesiveness – the extent to which different individuals or groups vote in a consistent pattern with each other. This can be demonstrated by a number of statistical means, most commonly regression analysis or environmental inference.

Community of Interest - A community of interest is a neighborhood or community that would benefit from being maintained in a single district because of shared interests, views or characteristics.

Although the preservation of "communities of interest" is required by many districting laws, the meaning of the term varies from place to place, if it is defined at all. The term can be taken to mean anything from ethnic groups to those with shared economic interests or workforce, to users of common infrastructure to those in the same media market. The Brennan Center for Justice provides a helpful summary of some of these uses.

Compactness - One of the "traditional" redistricting principles, low compactness is considered to be a sign of potential gerrymandering by courts, state law and the academic literature. More often than not, though, compactness is ill-defined by the "I know it when I see it" standard. Geographers, mathematicians and political scientists have devised countless measures of compactness, each representing a different conception, and some of these have found their way into law.

Contiguity - Like compactness, contiguity is considered one of the "traditional" redistricting principles. Most redistricting statutes mandate that districts be contiguous-- that is, they are a single, unbroken shape. Two areas touching at their corners are typically not considered contiguous. An obvious exception would be the inclusion of islands in a coastal district.

Cracking - A form of voter dilution occurring when districts are drawn so as to divide a geographically compact minority community into two or more districts. If the minority community is politically cohesive and could elect a preferred candidate if placed in one district but, due to cracking, the minority population is divided into two or more districts where it no longer has any electoral control or influence, the voting strength of the minority population is diluted.

Crossover Districts - A crossover district is one in which ethnic or language minorities do not form a numerical majority but still reliably control the outcome of the election with some similarly-minded majority voters crossing over to vote with the minority group.

CVAP (Citizen Voting Age Population) - An estimate of the raw number or percentage of 18-and-older citizens provided by the U.S. Census through the American Community Survey. This number represents the amount of potential voters that could be active in elections – an important measure in voting rights act cases.

CVAP is an estimate, and as with other Census Bureau estimates it comes with a margin of error. In an area as large as an LAUSD district, the margin of error will be fairly small.

Deferrals – In an election area where there are four-year terms, and elections every two years, a redistricting will result in a situation where a voter is set to elect a representative in the coming election, then a redistricting happens and their district changes to one that is not up for two more years. When their incumbent representative retires, they don’t have the opportunity to vote on a new representative. Technically, in this situation, they have no representative – their old representative moved to a different area and they have not yet had a chance to elect a new representative under the redistricted system. Their right to representation has been deferred for two years. For the opposite, see Accelerations.

Deviation – The deviation is any amount of population that is less than or greater than the ideal population of a district. The law allows for some deviation in state and local redistricting plans.

Dispersion – within compactness calculations, dispersion-based measures, such as the Reock and convex hull measures, evaluate the extent to which a shape's area is spread out from a central point. A circle is very compact, while a barbell is less compact.

Districted Elections – A system in which geographic boundaries are created for the purposes of elections. The most common type is a single-member district where the one elected official who represents that district is elected only by those who reside in the district. Two other common forms are multi-member districts, wherein the voters will elect two or more representatives from their area, and at-large election areas, where the representative must live in the area, but all voters participate in the election, not just residents of the area.

Effective minority district – a distinction between a district with the density of minority voting population necessary for that community to election a candidate of choice, and a district that technically meets the 50% threshold, but does not provide an advantage in elections. In very rare cases, a district can be considered an effective minority district at a measure below the 50% threshold.

Ecological Inference (EI) – A popular statistical method used to identify polarized voting and make projections about the voting patterns of an area based on data regarding past elections and the ethnic or other composition of the electorate.

Functional Contiguity - when areas are contiguous by how they relate to the community.  Two sides of a mountain pass may not be functionally contiguous, even if literally contiguous, and an island may not be literally contiguous, but be functionally contiguous to the shore of the mainland.

Gerrymandering - the process by which district boundaries are drawn to confer an electoral advantage on one group over another. The term is a portmanteau word formed from the surname of Massachusetts Governor Elbridge Gerry and the salamander shape of the district he approved, which appeared in an 1812 cartoon. Gerrymandering can take on many forms.

Gingles Factors - The Gingles factors are three preconditions set forth by the U.S. Supreme Court in Thornburg v. Gingles, 478 U.S. 30 (1986), that a minority group must prove to establish a violation of Section 2 of the Voting Rights Act.

GIS (Geographic Information Systems) – Rooted in the science of geography, GIS integrates many types of data into a spatial location and organizes layers of information into visualizations using maps and 3D scenes.

Group Quarters – As defined by the census, Group Quarters are places where people live or stay in a group living arrangement. These places are owned or managed by a third party that provides residents with housing and services. Examples include: Nursing facilities, prisons, and university dormitories. See: Prison Population Reallocation

Handshake Gerrymander - a form of an incumbent gerrymander between candidates of different parties who agree to an incumbent gerrymander, often in exchange for other votes or policy/political favors.

Ideal population - The ideal population is the number of persons required for each district to have equal population. The ideal population for each district is obtained by taking the total population of the jurisdiction and dividing it by the total number of districts in the jurisdiction. For example, if a county’s population is 10,000 and there are five electoral districts, the ideal population for each district is 2,000.

Incumbent / Incumbency – The current elected official. Incumbents and candidate addresses are not allowed to be a community of interest in California for the purpose of redistricting at the state, county or city jurisdictional levels.

Incumbent Gerrymander - the drawing of lines in a way that manipulates the process and divides communities in the name of protecting the interests of incumbent elected officials.

Indentation - Perimeter-area based measures of compactness, like the Polsby-Popper and Schwartzberg measures, can utilize indentation of district boundaries as a part of the calculation. Shapes with a smooth perimeter are more compact, while those with a contorted, squiggly perimeter have more indentations and are less compact.

Majority-minority district - a district in which racial or ethnic minorities comprise a majority (50%-plus-1 or more) of the population.

Metes and Bounds – A written description of district lines used in tandem with maps and other data and in some counties used as the official determination of district lines. These files are known for overly specific wording, such as “walk through the middle of the stream,” and “continue through the area between the vacant lot and the open field.”

Minority-coalition district - a type of majority-minority district in which two or more minority groups combine to form a majority in a district.

Minority Influence district - An influence district is one that includes a large number of minority voters but fewer than would allow the minority voters to control the election results when voting as a bloc. Minority voters are sufficient in number in “influence districts” to influence the outcome of the election.

Minority opportunity district – a district that provides minority voters with an equal opportunity to elect a candidate of their choice regardless of the racial composition of the district.

Minority vote dilution – when minority voters have their voting power weakened through an election structure or other means that deprives them of an equal opportunity to elect a candidate of choice. It is prohibited under the Voting Rights Act of 1965. Examples of minority vote dilution include cracking, packing, and the discriminatory effects of at-large election systems.

Nesting – The placing of districts within districts. This is most common in legislative maps where some states place two lower-house members within each single upper-house district. California has a lower-tiered requirement for nesting in legislative districts, however in 2011 this rule was barely followed.

One-person, one-vote – The constitutional requirement that requires each district to be substantially equal in total population. The principle is based on the mathematical assumption that one person in a district with 10 people has more of a voice in our democracy than one in a district with 10,000 people.

Packing – A form of vote dilution prohibited under the Voting Rights Act where a minority group is over concentrated in a small number of districts. For example, packing can occur when a minority population is concentrated into one district where it makes up 90% of the district, instead of two districts where it could be 50% or more of each.

Point Contiguous – when a district is connected only by two corners touching.

PL 94-171 – The eponymous federal law that requires the United States Census Bureau to provide states with data for use in redistricting and mandates that states define the census blocks to be used for collecting data. This is also used as the name for the U.S. Census dataset released every 10 years under the law.

Precinct - An area created by election officials to group voters for assignment to a designated polling place so that an election can be conducted. Precinct boundaries may change several times over the course of a decade. Several counties have transitioned away from precinct-based voting locations in exchange for county-wide vote centers, however the precinct is still a basis for determining what elections any voter can cast a ballot in, and they are how counties report election results.

Preclearance - The process of seeking review and approval from either the U.S Department of Justice or the federal court in the District of Columbia by jurisdictions that are covered under Section 5 of the Voting Rights Act.

Prisoner Population Reallocation – the act of shifting incarcerated population from where they reside on April 1st according to census data to their last known residential address or location of their arrest, simply for the purposes of defining the size of a census block.

Racially polarized voting or racial bloc voting – Patterns of voting along racial lines where voters of the same race support the same candidate who is different from the candidate supported by voters of the majority population. These have slightly different interpretations in the federal and state voting rights acts.

Reapportionment – The process of allocating seats in a legislative body to geographical areas, such as the U.S. Congress, where the number of seats in the House of Representatives is fixed at 435 and the number of seats allocated to each state is reevaluated following each decennial census.

Retrogression – A change in districting boundaries that puts minorities in a worse position under the new scheme than under the existing one. A key measure in Section 5 preclearance by the Department of Justice.

Section 2 (of the Voting Rights Act) – A key provision that protects minority voters from practices and procedures that deprive them of an effective vote because of their race, color, or membership in a particular language minority group. Districts covered under Section 2 include those where an ethnic or language minority is 50% or more of the citizen voting age population (CVAP) based on the current lines.

Section 5 (of the Voting Rights Act) – prohibits jurisdictions covered by Section 5 from adopting voting changes, including redistricting plans, that worsen the position of minority voters. This act is inactive after the Supreme Court invalidated the coverage formulas of Section 4.

Shapefiles – Electronic files that are used in GIS applications to identify shapes, generally of district boundaries or election areas, but they can also be used to identify physical geography, communities of interest, landmarks, and other features on a map.

Sociological gobbledygook – a term used by Supreme Court Chief Justice Roberts to discredit political science and mathematical tools used to quantify partisan gerrymandering.

String Contiguous – when a district is made contiguous by an area which is long and narrow, often unpopulated, such as a freeway or major road.

TIGER – Topologically Integrated Geographic Encoding and Referencing (TIGER) is the geographic basis of the census.  The files do not contain the census demographic data, but merely the geospatial/map data.

Undercount – The number of Americans missed in the census.

Vote Dilution - any structure or voting / elections method that has the effect of weakening the voting power of a group or community.

Voting age population – Residents calculated in the census that are over 18 years old, irrespective of their citizenship.

Voting Rights Act - The U.S. Voting Rights Act of 1965 was a landmark piece of civil rights legislation that outlawed discriminatory voting practices-- racial gerrymandering among them-- that had been used to disenfranchise African Americans. See: California Voting Rights Act

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