AP Elections Map Files Reference Guide

Overview

AP Elections Map Files are GeoJSON files designed to be joined with AP Elections results data. These files include the 50 states and the District of Columbia and are available for even election years from 2012 through 2026.

The following geographies are provided:

RU. AP Level 2 reporting units: New England towns and cities, Alaska State House districts and counties in other states.
CD. Congressional districts.
CD-RU. Congressional districts and AP reporting units.
CD-county. Congressional districts and counties.
County. Counties and county equivalents (equal to reporting units outside New England and Alaska).
SLDU. State legislative districts, upper chamber (most commonly State Senate).
SLDL. State legislative districts, lower chamber (most commonly State House).

Map File Release Notes

Map file release numbers correspond to the year of release. Version 1.x includes all map file releases in 2026.

September 28, 2026: Version 1.6

Updates the 2026 files to incorporate:

Removal of new CD boundaries in Missouri that were used in the August 4, 2026 primary election and later reverted by the state. The August primary election boundaries remain available in Map Files version 1.5.
Removal of new SLDU boundaries in Alabama that were used in the May 19, 2026 primary election and later reverted by the state. The primary election boundaries remain available in Map Files version 1.5.
New SLDU and SLDL boundaries in Mississippi, first used in 2025 special general elections that AP did not tabulate.
Minor SLDU and SLDL boundary changes in Minnesota, reflecting municipal boundary shifts.
Minor geography cleanup of CD-RU files in Massachusetts.

August 7, 2026: Version 1.5

Adds a supplemental file for 2026 New Hampshire House of Representatives floterial districts, 2026-sldl-nh-floterial.
Minor style edits to districtName field in New Hampshire in sldl files, all years.

July 20, 2026: Version 1.4

Updates the 2026 RU and CD-RU files to incorporate new Level 2 reporting units in Alaska.

June 4, 2026: Version 1.3

Updates the 2026 files to incorporate newly-passed congressional districts in Louisiana.

May 20, 2026: Version 1.2

Updates the 2026 files to incorporate newly-passed congressional districts in Alabama and Tennessee.

May 7, 2026: Version 1.1

Updates the 2026 files to incorporate:
- Newly-passed congressional districts in Florida.
- Newly-released 2025 Census cartographic boundary files.
Updates the CD-RU and RU files in all years to include IDs of newly reorganized Maine reporting units.
Updates the state legislative district files in all years with a minor revision of the GeoJSON layer name.

April 10, 2026: Version 1.0

Initial release.

Geographic Resolution

The files are primarily based on U.S. Census Bureau cartographic boundary shapefiles. Cartographic boundaries use simplified geographies and clipped coastlines for map presentation and are not suitable for geospatial analysis.

Two sets of resolutions are provided:

High resolution (highres). Uses Census 1:500,000 (500k) resolution files.
Low resolution (lowres). Further simplified to reduce file size and boundary complexity without removing any reporting units. Some very small islands are removed.

Boundaries for Hawaii are clipped to exclude the Northwestern Hawaiian Islands.

Map File Fields

Descriptions

Field Name	Description	Type	Used in These Files
stateFips	State FIPS code	String (2 digits)	All files
statePostal	USPS postal code	String (2 letters)	All files
districtFips	Legislative district FIPS code	String 2 digits for congressional districts 3 characters for state legislative districts	cd-ru, cd-county, cd, sldu, sldl
districtName	Legislative district name	String	cd-ru, cd-county, cd, sldu, sldl
countyName	County name	String	cd-ru, cd-county, ru, county
countyFips	State + county FIPS code	String (5 digits)	cd-ru, cd-county, ru, county
cousubFips	County subdivision FIPS code	String (5 digits) null outside New England states	cd-ru, ru
resportingunitID	AP reporting unit ID code	String	cd-ru, cd-county, ru, county
reportingunitName	AP reporting unit name	String Same as countyName outside New England	cd-ru, ru
geoid	Unique geographic identifier	String CD-RU files: 12 digits in New England: countyFips + districtFips + cousubFips 7 digits in Alaska: 0 + reportingunitID + districtFips 7 digits where cousubFips is null outside New England: countyFips + districtFips CD-county files: countyFips + districtFips (7 digits) CD files: stateFips + districtFips (4 digits) SLDU and SLDL files: stateFips + districtFips (5 characters)	cd-ru, cd-county, cd, sldu, sldl

Examples

Fields in a CD-RU file (New England state)

"stateFips": "25",
"statePostal": "MA",
"districtFips": "07",
"districtName": "District 7",
"countyFips": "25025",
"countyName": "Suffolk County",
"cousubFips": "07000",
"reportingunitID": "22035",
"reportingunitName": "Boston",
"geoid": "250250707000"

Fields in a CD-RU file (state with county-based RU)

"stateFips": "49",
"statePostal": "UT",
"districtFips": "01",
"districtName": "District 1",
"countyFips": "49035",
"countyName": "Salt Lake County",
"cousubFips": null,
"reportingunitID": "45018",
"reportingunitName": "Salt Lake County",
"geoid": "4903501"

Fields in a CD-RU file (Alaska)

"stateFips": "02",
"statePostal": "AK",
"districtFips": "00",
"districtName": "At-Large District",
"countyFips": "02000",
"countyName": null,
"cousubFips": null,
"reportingunitID": "2003",
"reportingunitName": "State House District 1",
"geoid": "0200300"

AP Reporting Units

The RU files include AP Level 2 reporting units, which are used in most AP Elections data:

Census county subdivisions (generally towns and cities) in New England: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island and Vermont.
State House districts in Alaska beginning in the 2026 election year files.
A single statewide Alaska unit (reportingunitID 2001) in files for election years prior to 2026.
Counties and county equivalents in all other states.

A small number of county subdivisions in Maine, New Hampshire and Vermont, as well as Kalawao County, Hawaii (FIPS code 15005), do not have AP reporting units. These areas have no or few residents.

District of Columbia wards (District Council/State Senate districts) are Level 3 reporting units in AP data and can be mapped using the SLDU files.

Alaska

AP results data and most map files for Alaska in election years prior to 2026 use a single Level 2 reporting unit that represents the entire state (reportingunitID 2001).

Beginning with Alaska’s August 18, 2026 primary election, substate results at the State House district level will be included in AP results data for statewide races, including U.S. House At-Large District, U.S. Senator and Governor. Those new Level 2 reporting units can be mapped using the CD-RU and RU files using file vintages 1.4 or later. For more information, see Alaska reporting units.

Non-statewide races, including State House and State Senate, will continue to be tabulated using Level 2 reportingunitID 2001.

Election results are not tabulated for county-equivalents in Alaska. The CD-county and County files include a statewide Alaska shape. Those files use reportingunitID 2001 for election years prior to 2026 and no reportingunitID beginning in 2026.

Legislative Districts

Results data for congressional district and state legislative district races can be joined to the map files using the U.S. Census Bureau’s district codes. This field is called districtFips field in the map files and censusDistrict in the AP Elections API.

Geography Names

The reportingunitName field in these files may differ in formatting from names used in the AP Elections API, particularly for years prior to 2026 and in some parts of New England. For additional context, see Spring 2026 Reporting Unit Updates. This field is populated even when no reporting unit exists.

The geography names in the map files are standardized as follows.

County Names

County names are defined by the Census Bureau.

County Subdivision Names

In New England, county subdivision reportingunitName values are based on the Census Bureau names with the following modifications:

The suffixes "town," "city," "Town city" and "township” are removed. For example, "Boston city" becomes "Boston."
- Town and city suffixes are retained when necessary to distinguish separate reporting units in Vermont with otherwise identical names; for example, "Barre city" and "Barre town."
- Other suffixes such as "gore," "purchase" and "location" are retained.
The Census abbreviation "UT" (used in Maine) is spelled out as "unorganized territory." For example, "Central Somerset UT" becomes "Central Somerset unorganized territory."
The suffix "plantation," used in Maine, is capitalized to "Plantation" in accordance with state and local norms.

Congressional District Names

Congressional districts are named either "District X" or "At-Large District."

State Legislative District Names

State legislative districts are generally named "District X." While this is usually a number, some districts use a letter or letter-number combinations (for example, "District 42," "District 42B" or "District H.")
Upper chamber districts in the District of Columbia are named "Ward X."
Massachusetts and Vermont upper and lower state legislative districts and New Hampshire lower districts use descriptive names, such as "District Addison-4" based on state and Census Bureau district names.

For a full list of state legislature districts with unconventional names, see Elections API documentation.

Special Cases

Two county subdivisions in Maine have modified names in the Map Files.

Penobscot Indian Island Reservation (cousubFips 57936) is split across two counties: Aroostook (countyFips 23003) and Penobscot (countyFips 23019). The populated portion, in Penobscot county, has reportingunitidID 20285 and is named "Penobscot Nation Voting District" per state and local election offices. The unpopulated portion, which consists solely of water in Aroostook County, is named "Penobscot Indian Island Reservation (water)."

File Vintages

The files are generally based on the corresponding year's Census Bureau cartographic boundary files.

Each year, the Census Bureau makes minor geographic boundary adjustments and updates a small number of county subdivision (town or city) FIPS codes. Full details are available in the Census Bureau's Boundary and Annexation Survey reference files. Also see their list of substantial changes to county and county-equivalent boundaries.

The sections below describe where AP Map Files differ from Census Bureau geographies.

2026 Files

The 2026 files are generally based on the most recent vintage of cartographic boundaries, currently 2025. When newer boundaries are released, the files will be updated accordingly.

The 2026 congressional district (CD) files incorporate newly redistricted boundaries in Alabama, California, Florida, Louisiana, North Carolina, Ohio, Tennessee, Texas and Utah. These shapes were constructed using block equivalency files and shapefiles provided by the states.

Missouri used new CD boundaries in the August 4, 2026 primary election. The state later reverted these changes. To access the August primary election CD boundaries, use Map Files version 1.5. Use version 1.6 or later to access the general election boundaries.

The 2026 state legislative district files include new upper-chamber (SLDU) district boundaries in Michigan, Minnesota and Mississippi and new lower-chamber (SLDL) district boundaries in Minnesota and Mississippi based on block equivalency files provided by those states and the Census Bureau.

The new Mississippi SLD boundaries were first used in 2025 special general elections that AP did not tabulate. The Minnesota district changes are very minor and reflect municipal boundary line changes rather than redistricting.

Alabama used new SLDU boundaries for districts 25 and 26 in the May 19, 2026 primary election. The state later reverted these changes and held a new special primary with the previous boundaries on August 11, 2026, which AP did not tabulate. To access the May primary election SLDU boundaries, use Map Files version 1.5. Use version 1.6 or later to access the general election boundaries.

All newly redistricted shapes are constructed using 2020 Census blocks and county definitions, consistent with the data used during the redistricting process. Although county boundaries have changed in a small number of cases, states use 2020 county lines in their redistricting processes, and these files follow suit.

If additional states approve new legislative districts for 2026, the files will be updated accordingly.

2022 Files in New England

For Connecticut, the AP Map Files and AP Elections data use pre-2022 county definitions for 2022 and 2023. The Census Bureau replaced counties with planning regions beginning in 2022; AP adopted this change in 2024. Additional details are available in the Elections API documentation.

For Vermont, the 2022 AP Map Files are based on the 2023 Census cartographic boundary files to include Essex Junction city, VT (reportingunitID 46247). This newly incorporated city reported election results in 2022 but did not appear in Census files until 2023.

2020 Congressional and State Legislative Districts

North Carolina redistricted its congressional and state legislative district boundaries for 2020. Those shapes were constructed using block equivalency files provided by the state and 2010 Census blocks and county lines, consistent with the redistricting process.

No other states adopted new legislative boundaries for 2020. Districts in all other states are based on the 2020 cartographic boundary files, which reflect 2018 district boundaries.

2012 Files

The 2012 files are based on the 2013 cartographic boundary files because 2012 cartographic boundary files do not exist for all geographies. Differences between 2012 and 2013 geographies used in these files are minimal.

Appendix

There are four instances of county-congressional district (CD) slivers with general election U.S. House votes in AP’s election results database that do not have corresponding map shapes: three in Virginia from 2020–2024 and one in South Carolina in 2020. These votes are reflected in the states' certified vote databases, but do not align to their official congressional district boundaries. This information is provided for reference.

year	statePostal	districtFips	reportingunitID	reportingunitName	votes
2020	SC	05	41041	Richland	22
2020	VA	02	47125	Newport News	341
2022	VA	06	47010	Bedford	1
2024	VA	06	47010	Bedford	6