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: August 3, 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.

Who publishes the data

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

The layer matrix

39 layers — 11 political and legislative, 7 public safety, 9 schools, 12 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 11 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 Illinois Supreme Court district elects the justices sitting over this address. No roster is joined; the card links the court itself rather than naming justices from an unverifiable list. 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-board 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-board Which of Chicago's 20 elected school board districts covers the point, and who represents it. school-board-members.json — hand-curated and hand-verified, because no machine-readable roster is published for this board. City of Chicago.
City Wardward 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.
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-district 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 12 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 — 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. Name-only in most counties; where a county's GIS carries trustees or a district office, the card shows them. Cicero's library board comes from the Cook County Clerk's directory of elected officials (cook-library-trustees.json, rebuilt weekly by CI). The counties that publish a library-district layer.
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-precinct 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.
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.