“Nationwide” describes a footprint, not the contents of every row. County property records differ in field availability, naming, publishing schedules, parcel geometry, and local practice. A useful coverage review tests the exact places and fields your workflow depends on.
Start with the geography you will use
Write down the county or state list before comparing record counts. State totals can hide a missing county that matters to a portfolio. City names are also a poor unit for source coverage because assessors usually publish by county or county-equivalent jurisdiction.
PropertyLayer keys county products by a five-digit county GEOID. The coverage directory links to products marked available with a positive record count. Listings with fewer than 500 records remain available for review but are excluded from search indexes until coverage is verified.
Compare counts with care
A parcel count is not a count of homes, buildings, owners, or mailing addresses. One parcel can contain several buildings, and one owner can hold many parcels. Some source systems also publish tax lots or condominium interests in ways that differ from neighboring counties.
Use counts to spot large changes and confirm order of magnitude. Do not treat a count mismatch by itself as proof that records are missing. Ask what the source considers a record and whether the comparison uses the same vintage.
Measure the fields that drive the decision
Make a short acceptance list before looking at a sample. For an owner-mailing workflow, that list might include owner name, mailing address, parcel identifier, and situs address. For a flood-screening workflow, it might include geometry, FEMA flood zone, land area, and improvement value.
Field presence is the share of records where a field has a value. It is not a correctness score. A county can publish a field for nearly every parcel and still use conventions that need review. Another county may omit a field because its source does not collect it.
County coverage pages show available presence rates from the current catalog. Inspect the record values too, especially dates, identifiers, units, and coded fields.
Check provenance and time
Record the source, extraction date, tax year, and any field-specific dates. Assessment values, sales, building attributes, boundaries, and mailing addresses can move on different schedules. “Updated” should identify what changed and when the underlying county published it.
PropertyLayer preserves source dates where they are available and uses null when a source value is absent. The public field reference shows the standardized record structure.
Test the delivery you plan to operate
A sample should resemble the paid file or API response in names, types, null behavior, and geometry format. Load it with the same parser, database, or GIS that production will use. Check large identifiers as strings, dates with missing month or day values, coordinate order, and geometry validity.
For API work, test normal requests, no-result requests, invalid inputs, pagination, and rate-limit handling. For bulk work, test decompression, import time, indexes, joins, and replacement of an older delivery.
Write an acceptance note
End the review with a short record of the approved geography, required fields, tolerated null rates, accepted source dates, and delivery format. This prevents a broad marketing label from becoming the specification for a production system.
Standards and further reading
- The U.S. Census Bureau defines counties and county-equivalent entities, including Alaska boroughs and census areas, Louisiana parishes, independent cities, and the District of Columbia.
- The IETF’s GeoJSON standard defines geometry types, coordinate order, and interoperability requirements for GeoJSON deliveries.
- The Open Geospatial Consortium publishes the GeoPackage standard for portable SQLite-based geospatial data.