Illinois sources & data layers

Every layer in districtry Illinois, and exactly where its data comes from.

← Back to the map 🧩 What data is missing?

This app is a reader over other people's data. It draws no boundary of its own and names no officeholder it cannot cite, so the useful question about any answer it gives is who published this, and when. That is what this page is for: the publishers the app credits as a whole, then one row per layer naming the source behind that layer specifically.

Not for legal or official use. Boundary and roster data come from public sources that explicitly disclaim legal precision. Always confirm district assignments and officeholders with the relevant government office before relying on them for anything official.

Data last verified: September 11, 2026

Where a source publishes nothing, the app says so rather than guessing — the missing-data panel on the map is the standing list of what nobody publishes yet, and what would close each gap.

This page says where each answer comes from today. What has changed here since the app launched, and when, is its own record: the history page.

Who publishes the data

The upstream publishers this app depends on, across all layers. Per-layer provenance is in the matrix below.

City of Chicago data

The City of Chicago's Data Terms of Use ask every application built on data from its portal to carry the statement below. It is reproduced exactly as the City wrote it.

“This site provides applications using data that has been modified for use from its original source, www.cityofchicago.org, the official website of the City of Chicago. The City of Chicago makes no claims as to the content, accuracy, timeliness, or completeness of any of the data provided at this site. The data provided at this site is subject to change at any time. It is understood that the data provided at this site is being used at one’s own risk.”

The layer matrix

41 layers — 12 political and legislative, 7 public safety, 9 schools, 13 geography and amenities. Each row names the publisher the boundary comes from, where the names on the card come from, and the ground the layer actually answers on — outside that ground the layer hides itself rather than guessing.

Political & legislative 12 layers

Districts that elect somebody — from your ward to your seat in Congress.

LayerWhat it answersBoundary sourceWho it namesWhere it applies
IL Supreme Court Districtil-supreme-court Which of the five Illinois judicial districts this address sits in — the district that elects its Supreme Court justice and holds the Appellate Court branch hearing its appeals. The justices, from the courts' own site — illinoiscourts.gov's Meet the Justices page for the Supreme Court and its Judicial Directory for the Appellate Court, rebuilt weekly. Illinois — statewide.
U.S. House Districtcongress The U.S. House district covering the point, and the representative holding it. congress-roster.json, rebuilt weekly by CI from the public-domain unitedstates/congress-legislators dataset — including each member's district office and Washington office. Illinois — statewide.
IL State Senate Districtil-senate The Illinois State Senate district covering the point, and the senator holding it. il-senate-members.json, rebuilt weekly by CI from the Illinois General Assembly's member pages. Illinois — statewide.
IL State House Districtil-house The Illinois State House district covering the point, and the representative holding it. il-house-members.json, rebuilt weekly by CI from the Illinois General Assembly's member pages. Illinois — statewide.
Judicial Subcircuitjudicial-subcircuit The judicial subcircuit that elects circuit judges for this address, in the counties divided into them. No roster is joined; each card links the circuit court that seats the judges. The counties that divide their circuit into subcircuits.
County Board Districtcounty-boardWho is my county commissioner? The county board district covering the point, and the commissioner or board member elected from it. Cook joins the county's own live elected-officials table on the same server. Every other county joins a roster rebuilt weekly by CI from that county's own board page — two counties whose boards publish nothing online ride a document their clerk sent, and the refresh says so out loud rather than implying it was re-read. The counties that publish board-district boundaries — county by county in COUNTY_STATUS.md.
Cook County Board of Review Districtccbr Which of the three Cook County Board of Review districts hears property-tax appeals from this address, and the commissioner elected to it. ccbr-roster.json, rebuilt weekly by CI from cookcountyboardofreview.com. Cook County.
Elected School Board Districtschool-boardWhat school board district am I in? Which of Chicago's 20 elected school board districts covers the point, and who represents it. school-board-members.json, rebuilt weekly by CI from the Board's OWN member index at cpsboe.org — every seat with its sub-district, the office a member holds where they hold one, a cps.edu address and a link to that member's own bio page, plus the Board's office and its city-wide President on every card. THIS FILE WAS HAND-CURATED UNTIL 2026-09-23 and this note said no machine-readable roster is published for this board, which was false and had let the file drift: District 9a shipped the bare string VACANT where the Board names its Vice President, and District 10b named a member who resigned in March 2026. The two publishers number the same seats differently — the boundary calls them 1..20 and the Board calls them 1A..10B — so the builder joins them on the shipped geometry's own sub-district label, and the Board's index and each member's bio page must agree on name, office and district before anything is written. City of Chicago.
City WardwardWho is my alderman? The ward covering the point and the alderperson or council member elected to it — in Chicago, and in the suburbs that also elect by ward. Chicago's alderpersons come from a live join against the city's own roster dataset (htai-wnw4); each suburban ward's holder comes from municipal-officials.json. Chicago, plus the suburban municipalities that elect by ward.
Ward Precinctward-precinct The Chicago ward precinct containing the point — the smallest unit the city runs elections in. Nobody is elected from a precinct; it is an election unit, not an office. City of Chicago.
Tribal Governmenttribal-government Whether this address is on tribal land, and which nation's government answers for it — Illinois has one such area, near Shabbona in DeKalb County. The council, from the nation's own published council page, read weekly by scripts/tribal_council_scraper.py and dated on the card: seven members with their office, term and telephone. The government, its seat and its website come from the Bureau of Indian Affairs' tribal leaders directory (data/bia-tribal-governments.json); the land is joined to the government by this project's own data/tribal-government-join.json. Illinois — one area, in DeKalb County. Almost every point in the state is on no tribal land.
Early Voting Siteearly-voting The early voting sites nearest the point — which double as the secured ballot drop boxes. No officeholder; each row names the site. City of Chicago, and only while early voting is running for an election.

Public safety 7 layers

Who answers a call at this address, and where they answer it from.

LayerWhat it answersBoundary sourceWho it namesWhere it applies
Fire Protection Districtfire-district The fire protection district responsible for this address, where fire service is a special district rather than a municipal department. Most counties publish no trustee roster alongside the boundary, so most cards name the district only; where a county's GIS carries district contact details, the card shows them. The counties that publish a fire-district layer.
DuPage Special Police Districtdupage-county-special-police Whether the point sits in one of DuPage County's special police districts — the tax districts that fund sheriff's patrol in unincorporated areas. No district officeholder exists — policing is by the elected DuPage County Sheriff, whom the card links. DuPage County.
Police Districtpolice-districtWhat police district am I in? The Chicago police district covering the point, and its station. cpd-district-info.json, rebuilt weekly by CI from chicagopolice.org, with the station's address and phone joined from CPD's own station layer. City of Chicago.
Police Beatpolice-beat The Chicago police beat containing the point — the patrol unit inside a district. No officeholder — a beat is a patrol unit. City of Chicago.
CCPSA District Councilccpsa-district-council The elected District Council for this police district, under the Community Commission for Public Safety and Accountability. ccpsa-district-councils.json, rebuilt weekly by CI. City of Chicago.
Police Stationpolice-station The three police stations nearest the point, by straight-line distance. No officeholder; each row names the station. The whole covered area.
Fire Stationfire-station The three fire stations nearest the point, by straight-line distance. No officeholder; each row names the station. The whole covered area.

Schools 9 layers

The district, the attendance zone, and the schools nearest the point.

LayerWhat it answersBoundary sourceWho it namesWhere it applies
High School Districtschool-district-secondary The high school district serving the point, where elementary and high school districts are separate. No roster is joined; the card names the district. Illinois outside Chicago — inside the city, CPS is a single unified district.
Unified School Districtschool-district-unified The unified (K-12) school district serving the point. No roster is joined; the card names the district. Illinois — statewide.
Elementary School Districtschool-district-elementary The elementary school district serving the point, where elementary and high school districts are separate. No roster is joined; the card names the district. Illinois outside Chicago — inside the city, CPS is a single unified district.
CPS Network (High School, admin office)cps-hs-network The CPS high school network the point falls in, and the chief who runs it. The network chief, phone and address ride the dataset's own properties — no separate roster. City of Chicago.
CPS Network (K-8, admin office)cps-network The CPS elementary (K-8) network the point falls in, and the chief who runs it. The network chief, phone and address ride the dataset's own properties — no separate roster. City of Chicago.
CPS High School Zonecps-high The CPS high school this address is zoned to. No officeholder; the card drops a pin on the zoned school and links its CPS profile. City of Chicago.
CPS Middle School Zonecps-middle The CPS middle school this address is zoned to, where middle schools are zoned separately. No officeholder; the card drops a pin on the zoned school and links its CPS profile. City of Chicago.
CPS Elementary School Zonecps-elementary The CPS elementary school this address is zoned to. No officeholder; the card drops a pin on the zoned school and links its CPS profile. City of Chicago.
School Location (all, incl. private, nearest N)school-site The school campuses nearest the point, filterable by type — not a zone, a proximity list. No officeholder; each row names the school. City of Chicago.

Geography & amenities 13 layers

The boundaries that place an address without electing anyone, plus the nearest public services.

LayerWhat it answersBoundary sourceWho it namesWhere it applies
Countycounty Which Illinois county contains the point, who runs its elections, and — where the county elects its board countywide — the board members themselves. il-county-clerks.json, rebuilt weekly by CI from the Illinois State Board of Elections' election-authority directory, plus il-county-commissioners.json for the twelve counties that elect their board at large and so have no district geometry to show. Illinois — statewide.
Water Reclamation District (MWRD)mwrd Whether the point sits inside the Metropolitan Water Reclamation District of Greater Chicago. Nobody is elected from a sub-area: MWRD's nine commissioners are all elected district-wide, so the card links the board instead of naming a representative for the point. Cook County.
Township / County Subdivisiontownship The township or county subdivision containing the point — in Chicago, which of the city's eight townships the Assessor groups it in — and, in covered counties, the township's elected officers. township-officials.json, rebuilt weekly by CI from the Cook County Clerk's directory (29 townships — supervisor, trustees, clerk/assessor/collector/highway commissioner, hall contact), joined by county-subdivision GEOID. Townships in other counties keep the identity-only card. Illinois — statewide for the boundary; officials are carried for Cook County.
Municipalitymunicipality The city, village or town containing the point — or that it sits in unincorporated county — and the officials elected to run it. municipal-officials.json, rebuilt weekly by CI from county clerk directories across the covered counties, plus Chicago's own citywide officers. Illinois — statewide for the boundary; officials are carried for the covered counties.
Park Districtpark-district The park district serving the point, including the Chicago Park District. Name-only in most counties; where a county's GIS carries commissioners or a district office, the card shows them. The counties that publish a park-district layer.
Library Districtlibrary-district The public library district serving the point, and whether library service there comes from a district or a municipal fund. Four sources, all rebuilt weekly by CI. The district-governed libraries that file an Annual Financial Report with the Illinois Comptroller name their own board and administration on it (il-library-district-officials.json). Every library's own page in the Illinois library systems' shared directory names one administrator and links the library's site (il-library-contacts.json); it names no trustee, because that directory's staff lists and annual certifications are behind a sign-in. For the cards no filing answers for — the municipal and township libraries — a board of trustees is read off the library's OWN website, each record naming the page it came from and the day it was read (il-library-trustees.json). Where a county's GIS carries trustees or a district office the card shows them, and Cicero's library board comes from the Cook County Clerk's directory of elected officials (cook-library-trustees.json). The counties that publish a library-district layer, plus seven that publish none and are drawn from a statewide layer instead.
Community Areacommunity-area Which of Chicago's 77 community areas contains the point. No officeholder — a community area is a statistical and planning boundary, not a district anyone is elected from. City of Chicago.
ZIP Codezip-code The ZIP code area containing the point. No officeholder — a ZIP code is a postal delivery unit, not a government district. Illinois — statewide.
Voting Precinctcounty-precinctWhat precinct am I in? The voting precinct containing the point outside Chicago, and — where the county publishes it — the polling place that serves it. No officeholder. Where the county publishes polling places, the card names the one serving the precinct; where it publishes a board-district join, the card names that too. Suburban Cook County — city precincts belong to the Ward Precinct layer — plus the other counties that publish a precinct layer.
Special Service Areassa Whether the point sits inside a Special Service Area — a local property-tax district funding street cleaning, landscaping, security, marketing and façade programs beyond the city's baseline service — and which one. No elected body — an SSA is created by City Council ordinance and overseen by a commission the Mayor appoints with Council consent, with a contracted service provider agency delivering the work. The city's boundary dataset names neither, so the card names nobody and links the city's SSA program page. The City of Chicago — and most points in the city are in no SSA at all.
TIF Districttif-district Whether the point sits inside a tax increment financing district, and which one. No elected body — TIFs are created by municipal ordinance. The card shows the Clerk's agency number and links the Clerk's TIF reports. Cook County — and most points are in no TIF at all.
Post Officepost-office The three post offices nearest the point, by straight-line distance. No officeholder; each row names the office. The whole covered area.
Librarylibrary The three Chicago Public Library branches nearest the point. No officeholder; each row names the branch. City of Chicago.