Reference
Geographic layers
This page explains which geographies the app exposes, the choices we made to make those layers consistent across the country, and how to use them in URLs and comparisons.
Geographic layers in the app
The app exposes five layers. Four get full dashboards; tracts are used inside cards as a sub-municipality breakdown.
| Layer | Has dashboard | Notes |
|---|---|---|
nation | yes | US aggregate |
state | yes | 50 states + DC |
county | yes | Labeled "Parish" in Louisiana, "Borough" in Alaska, "Planning Region" in Connecticut |
municipality | yes | Cities, towns, villages, and consolidated city-counties; resolved per state (see below) |
tract | no | Used inside cards (sub-municipality breakdowns) and as the building block for project subareas |
A municipality can have more than one parent county when its boundary crosses a county line. Breadcrumbs walk every parent so the locality shows up under each county it spans.
Why "municipality" is its own layer
The Census Bureau publishes localities under two different layer names depending on the state. In Texas, Georgia, and most of the country, a city or town is an incorporated place. In New England (and a handful of other strong minor-civil-division states), the equivalent locality is a county subdivision. The same locality can also appear in both layers at once, and a handful of consolidated city-counties (Indianapolis, Nashville, Honolulu, etc.) are not represented as cities in the Census place layer at all.
A service that wants to expose a consistent "local government" view has to reconcile this, otherwise users see a city listed as a place in one state, a county subdivision in another, both at once in a third, and missing entirely in a fourth. The app collapses all of this into a single user-facing layer called municipality, picking the right Census source per state, deduplicating overlaps, and adding the consolidated city-counties that Census omits.
For Census background on the underlying geography types, see the ACS geography concepts and definitions.
How we pick municipalities
The municipality layer pulls from different Census sources depending on the state:
- Most states — municipalities are incorporated places (cities, towns, villages, boroughs).
- Strong minor-civil-division states (Connecticut, Maine, Massachusetts, Michigan, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, Wisconsin) — municipalities are county subdivisions (towns/townships that function as governments). Where a place and a coterminous county subdivision both exist for the same locality, the county subdivision is used.
- Consolidated city-counties — seven localities are emitted as municipalities directly from their county geography because Census represents them as a "balance" record or has no city place at all: Indianapolis (IN), Nashville (TN), Louisville (KY), Athens (GA), Augusta (GA), Butte (MT), and Honolulu (HI).
- Census Designated Places (CDPs) are not municipalities and do not get dashboards. CDPs are unincorporated communities the Census delineates for statistical purposes; they have no government of their own.
The result: the count and identity of municipalities in a given county may differ from a raw Census place query. The app's count is the one that matches what a resident or planner would call a "city or town" in that state.
Using the layers
URL patterns:
| Page | URL pattern | Example |
|---|---|---|
| US dashboard | /dashboard | /dashboard |
| State dashboard | /dashboard/state/{geoid}/{slug} | /dashboard/state/25/Massachusetts |
| County dashboard | /dashboard/county/{geoid}/{slug} | /dashboard/county/25005/Bristol-County-MA |
| Municipality dashboard | /dashboard/municipality/{geoid}/{slug} | /dashboard/municipality/0644000/Los-Angeles-CA |
| Markdown render of any dashboard | append .md to the slug | /dashboard/county/25005/Bristol-County-MA.md |
| Single-card embed | /{layer}/{geoid}/cards/{chart_type} | /county/37179/cards/housing_affordability |
| US-aggregate card embed | /cards/{chart_type} | /cards/affordability_map |
| Card JSON | /{layer}/{geoid}/api/cards/{chart_type} or /api/cards/{chart_type} | /county/37179/api/cards/housing_affordability |
The {layer} segment in card embed URLs accepts state, county, municipality, or tract. Older URLs that exposed the underlying Census layer name (place, county subdivision) are preserved with 301 redirects, so external links and search results keep working. Comparison views (siblings, parent county) use the same layer names and so behave the same way in every state.