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Supported Counties — Property History Data Sources

Plotline fetches property sales and building permit records from county open data portals. Each county uses a different API: Denver and Adams use ArcGIS Feature Services, DC uses DCGIS ArcGIS REST services, Santa Clara (San Jose) uses CKAN, and New York County (Manhattan) uses Socrata.

Last verified: 2026-03-26

Denver County

Portal: https://opendata-geospatialdenver.hub.arcgis.com

Dataset Feature Service URL Key Fields Notes
Residential Construction Permits services1.arcgis.com/zdB7qR0BtYrg0Xpl/.../ODC_DEV_RESIDENTIALCONSTPERMIT_P/FeatureServer/316 ADDRESS, ADDRESS_NUMBER, ADDRESS_STREETNAME, DATE_ISSUED, CLASS, VALUATION, PERMIT_NUM, CONTRACTOR_NAME DATE_ISSUED is epoch-ms. ADDRESS_NUMBER is integer.
Commercial Construction Permits services1.arcgis.com/zdB7qR0BtYrg0Xpl/.../ODC_DEV_COMMERCIALCONSTPERMIT_P/FeatureServer/317 Same field structure as residential Separate layer for commercial permits
Real Property Sales Not available — Socrata dataset hmrh-5s3x was retired; no replacement on ArcGIS Hub

Address matching: Query uses upper(ADDRESS) LIKE '{number} %{street}%' to handle directional prefixes (e.g., "1437 N BANNOCK ST").

Adams County

Portal: https://data-adcogov.opendata.arcgis.com

Dataset Feature Service URL Key Fields Notes
Building Permits (Eye On Adams) services3.arcgis.com/4PNQOtAivErR7nbT/.../Building_Permits_Eye_On_Adams/FeatureServer/0 CombinedAddress, HouseNumber, StreetName, CaseOpened, TypeOfWork, ClassOfWork, Description, RecordID_ CaseOpened is epoch-ms. HouseNumber is integer.
Property Sales Not available — Old Socrata domain data.adcogov.org is defunct; no public sales API found

Address matching: Query uses upper(CombinedAddress) LIKE '{number} %{street}%'.

Coverage note: Adams County data only covers unincorporated areas. Municipalities like Thornton, Westminster, and Northglenn issue their own permits and do not publish them through the county portal.

District of Columbia

Portal: https://opendata.dc.gov (DCGIS ArcGIS REST services)

Dataset Service URL Key Fields Notes
Property Sales (ITSPE FACTS) maps2.dcgis.dc.gov/.../Property_and_Land_WebMercator/MapServer/56 PREMISEADD, SALEPRICE, SALEDATE ArcGIS MapServer layer
Building Permits (DCRA) maps2.dcgis.dc.gov/.../FEEDS/DCRA/MapServer/{layer} FULL_ADDRESS, ISSUE_DATE, PERMIT_TYPE_NAME, FEES_PAID Year-specific layers (2020–2026), queried in parallel

Address matching: Query uses upper(PREMISEADD) LIKE '%{number} {street}%'.

Santa Clara County (City of San Jose)

Portal: https://data.sanjoseca.gov (CKAN)

Dataset CKAN Resource ID Key Fields Notes
Building Permits (Active) 761b7ae8-3be1-4ad6-923d-c7af6404a904 ADDRESS, ISSUED_DATE, DESCRIPTION, VALUATION, STATUS CKAN Datastore API
Building Permits (Under Inspection) 89ccdad9-7309-4826-a5f3-2fcf1fcb20fa Same fields Separate dataset per status
Building Permits (Expired) df4b8461-0c7a-4d16-b85d-ff7f71c5fed5 Same fields
Property Sales Not available — No public API

Address matching: Filters by ADDRESS field using number + street name.

Coverage note: This adapter covers City of San Jose addresses only. Other cities in Santa Clara County (Sunnyvale, Mountain View, Cupertino, etc.) may have their own portals or no public data.

New York County (Manhattan)

Portal: https://data.cityofnewyork.us (Socrata / NYC Open Data)

Dataset Socrata Resource ID Key Fields Notes
Property Sales (Citywide Rolling Calendar) usep-8jbt address, sale_price, sale_date, building_class_category Filtered to borough 1 (Manhattan); excludes $0 sales
Building Permits (DOB Permit Issuance) ipu4-2q9a house__, street_name, issuance_date, job_type, permit_type Filtered to borough MANHATTAN

Address matching: Uses upper(address) LIKE '%{number} {street}%' for sales; house__='{number}' AND upper(street_name) LIKE '%{street}%' for permits.

Adding a New County

To add support for a new county:

  1. Find the county's open data portal (ArcGIS Hub, Socrata, or other).
  2. Locate building permits and/or property sales datasets.
  3. Identify the Feature Service URL and layer ID (or Socrata resource ID).
  4. Map the county's field names to our normalized schema.
  5. Create a new adapter class in backend/app/services/county_adapters.py:
    • Subclass CountyAdapter
    • Implement fetch_sales() and fetch_permits()
    • Map raw field names to PropertyEventData
  6. Register the adapter in COUNTY_ADAPTERS dict.
  7. Add the county to this document.
  8. Write tests for the new adapter's parsing logic.

ArcGIS Feature Service Notes

  • Query endpoint: {service_url}/query?where=...&outFields=*&f=json&returnGeometry=false
  • Date fields: Returned as epoch-milliseconds (divide by 1000 for Unix timestamp).
  • Integer fields: Don't quote numeric values in WHERE clauses.
  • LIKE queries: Use upper(FIELD) LIKE 'VALUE%' for case-insensitive matching.
  • Result limits: Default max varies per service (often 1,000–2,000 per request).

Socrata Notes (for future counties still on Socrata)

  • Field names are case-sensitive in SoQL queries.
  • Resource IDs change when datasets are republished.
  • Rate limits: 1,000 requests/hour without an app token, 10,000/hour with one. Set SOCRATA_APP_TOKEN in .env if needed.
  • Redirects: Enable follow_redirects=True — some portals redirect silently.