What boundaries-io does and who it is for
When you need to render a polygon on a map, find which county a GPS coordinate falls inside, or feed a zipcode list into a spatial analysis pipeline, you need pre-built boundary geometry — not just a latitude/longitude point. boundaries-io solves exactly that problem for the United States. It exposes 35 endpoints that return GeoJSON feature collections for every major administrative and statistical geography the US Census tracks: zipcodes, counties, cities and incorporated places, states, territories, neighborhoods, census tracts, and Nielsen DMA regions (on the top tier). The results drop straight into Google Maps Data Layer, OpenLayers, Mapbox, or any library that speaks GeoJSON.
The typical adopters listed by the provider span marketing analytics, insurance underwriting, emergency response routing, and transportation logistics — domains where knowing the exact polygon of a territory matters more than an approximate bounding box. That breadth of use case is reflected in the endpoint design: some routes answer point-in-polygon questions ("which county contains this coordinate?"), others handle bulk lookups ("give me boundaries for these 1,000 zipcodes"), and others resolve boundaries from identifiers like FIPS codes or H3 indexes.
Endpoint walkthrough
The 35 endpoints are grouped into eight functional families.
Zipcode boundaries
The most common entry point. A GET to /rest/v1/public/boundary/zipcode retrieves one or a handful of zipcode polygons by code. A radius-based route returns all zipcodes whose boundaries intersect a given point within a specified distance in miles. A WKT (Well-Known Text) POST lets you query by an arbitrary polygon or multipolygon — useful when you already have a drawn region and want to find which zipcodes overlap it. On PRO and above, a separate POST endpoint accepts a JSON array of up to 1,000 zipcodes in a single call, which is the right tool for bulk pre-processing jobs.
County boundaries
Four endpoints cover county data. The point-in-polygon route (/boundary/county/within) identifies the county for a lat/lon. A named route resolves a county by name and state abbreviation. A state-scoped names-only route is handy for populating a dropdown without fetching geometry. PRO subscribers and above can also POST a list of up to 20 county names to retrieve multiple boundaries at once.
State and territory boundaries
A state boundary endpoint returns a simplified GeoJSON polygon for a given state abbreviation. A territories endpoint covers all 57 US states and territories. A separate unitedstates route returns the outline of the entire country including territories — useful as a base layer.
Place boundaries
These endpoints correspond to US Census "Places" — both incorporated cities and unincorporated communities. You can look up a place by name and state abbreviation, query by location (point-in-polygon), or list all place names within a state.
Neighborhood boundaries
Neighborhood-level geometry is available by name and state, and via a point-in-polygon lookup. A combined route also accepts city and county filters alongside state.
Census tracts
Four census tract endpoints cover lookup by GeoId, bulk POST by a list of GeoIds, county-scoped retrieval, and point-in-polygon. These are the smallest geography in the API and are commonly used in demographic analysis and regulatory compliance workflows.
H3 hexagon support
The API integrates Uber's H3 geospatial indexing system. You can retrieve the H3 hexagon that contains a given location, look up a hexagon by its H3 index (as either a long integer or a hex string), calculate the distance and bearing between two H3 indexes, and convert between long and hex representations of an index. This is a niche but valuable addition for teams already using H3 for spatial partitioning.
DMA regions (MEGA only)
Nielsen Designated Market Area boundaries are gated to the MEGA subscription. Two endpoints return DMA region boundaries and region names by state. The provider notes that the underlying metadata is sourced from publicly available VAB data.
Pricing breakdown
All quotas reset daily. Every paid tier carries a $0.01 overage charge per request beyond the daily cap, so usage spikes won't cut off your application — they just accrue cost.
| Plan | Monthly price | Daily request cap | DMA endpoints | Batch zipcode (1,000) |
|---|---|---|---|---|
| BASIC | $0 | 50 | No | No |
| PRO | $35 | 5,000 | No | Yes |
| ULTRA | $79 | 30,000 | No | Yes |
| MEGA | $195 | 200,000 | Yes | Yes |
The BASIC plan is explicitly described as a 7-day trial. At 50 requests per day it is enough to verify integration and test your rendering pipeline, but insufficient for any production workload. The jump to PRO at $35/month buys 5,000 daily requests plus the bulk zipcode and multi-county POST endpoints — a meaningful unlock for apps that process batches. ULTRA at $79/month raises the cap six-fold to 30,000, covering moderate production traffic. MEGA at $195/month is the recommended tier, delivering 200,000 daily requests and the DMA boundary endpoints unavailable elsewhere.
The flat $0.01 overage rate is straightforward to budget around: 10,000 overage calls cost $100. Teams with highly variable daily traffic should model their 95th-percentile day rather than their average when choosing a tier.
Practical use cases
- Territory management tools: Sales or field-service apps that let users draw or select a territory and compute which zipcodes or counties fall inside it can use the WKT POST endpoint on the backend.
- Address enrichment pipelines: Given a list of addresses geocoded to lat/lon, batch county and census tract lookups add demographic context for insurance rating or marketing segmentation.
- Emergency dispatch systems: Real-time point-in-polygon queries against county or place boundaries determine which jurisdiction to route a call to.
- Delivery zone configuration: E-commerce and logistics platforms use zipcode radius queries to define serviceable areas dynamically.
- H3-based analytics: Teams using H3 for hexagonal binning of event data can use boundaries-io to tie H3 cells back to named administrative geographies.
Limitations and things to check before integrating
US-only data. Every endpoint covers the United States (and its territories). There is no international boundary data.
No harvesting. The provider explicitly prohibits using the API to systematically download the entire dataset. If you need raw boundary files for offline use, they point to the US Census TIGER data dump directly. The API is intended for on-demand, application-driven queries.
Daily quota resets, not monthly. Unlike APIs that pool a monthly quota, boundaries-io resets every day. A batch job that consumes its entire daily allowance in the first hour will be blocked until midnight regardless of how many days remain in the billing cycle. Design your scheduling accordingly.
UI latency warning. The provider notes that testing large result sets through the RapidAPI/Mashape browser UI introduces significant latency. The 202 ms average latency figure applies to programmatic calls; interactive UI testing of bulk endpoints will feel slower.
DMA data is unofficial. The Nielsen DMA boundaries are described as "unofficial" and sourced from publicly available third-party data, not directly licensed from Nielsen. Verify suitability for any commercial media-buying application.
Tier-gated endpoints. Multi-county POST and bulk zipcode POST require PRO or above. DMA endpoints require MEGA. Hitting a gated endpoint on a lower tier will return an error, so check your subscription level when building integrations that use those routes.
Getting started
- Subscribe to the BASIC plan to get your API key and explore the endpoint responses against real data.
- Paste GeoJSON responses into geojson.io to visually verify the shapes you're receiving before writing rendering code.
- Test bulk endpoints (zipcode array POST, multi-county POST) programmatically rather than through the browser UI — the provider calls this out explicitly for performance reasons.
- Assess your daily call volume against the tier table above, factoring in peak days, to choose the right subscription before going to production.
- For questions or MEGA-tier feature requests, the provider offers 24/7 support at [email protected].
