What Is an APN (Assessor Parcel Number)?
The APN is the closest thing a piece of land has to a Social Security number — one stable ID that ties all its records together.
Definition
An Assessor Parcel Number (APN) — also called a parcel number or parcel ID — is the unique identifier a county assigns to every parcel of land in its jurisdiction. It's the primary key that connects a property across tax records, deeds, building permits, and ownership history.
How it's structured
Most APNs are a hyphenated numeric string (e.g. 01-3209-014-0230) that encodes geographic information — often a map book, page, and parcel position. Formats vary by county, so an APN is only guaranteed unique within its county. Pairing it with the county FIPS code makes it unique nationwide.
Why it matters
The APN is stable — it stays with the parcel, not the owner, and doesn't change when the property is sold (only when a parcel is physically split or merged). That stability makes it the most reliable way to identify a specific piece of land and to join records from different sources.
In this dataset
Every row carries its parcel_apn and county_fips (see the data dictionary), so you can match our data against county assessor records or your own systems. Each row also carries a stable id; query that property's current state through the Straply API with GET /property/{id}.
Frequently asked
What is an APN?
How do I find my property's APN?
Does the APN change when a property is sold?
Is the APN unique nationwide?