How to Access Public Parcel Data via GIS

Parcel data — the legal boundaries of property ownership — is one of the most valuable datasets in GIS. It is used for real estate analysis, urban planning, environmental regulation, and tax assessment.

Where Does Parcel Data Come From?

In the United States, parcel data is almost always maintained at the county level by the Assessor's Office or the County GIS Department.

• Assessor: Maintains ownership and tax records.
• GIS Department: Maintains the spatial polygons representing the parcel boundaries.

How to Find Parcel Data

Search for your county's GIS portal using search queries like "County Name GIS" or "County Name Assessor Parcel Map".

Look for a "Download" or "Open Data" link on the county website. Many counties now publish their data on ArcGIS Online.

Downloading Parcel Data from ArcGIS REST Services

If the county publishes its parcel data as an ArcGIS REST FeatureServer, downloading it is easy and free.

1. Locate the Parcels layer in the county's ArcGIS portal or open data site.
2. Copy the FeatureServer URL for that layer.
3. Open Geo Server Data Downloader.
4. Paste the URL and click Add Layer.
5. Export the data as a Shapefile, GeoPackage, or CSV.

Understanding the Attributes

Parcel data usually includes an Assessor Parcel Number (APN) and various ownership details. You can use the APN to join the spatial data with other tax or ownership databases.

Data Limitations

Be aware that parcel data is often updated on a lag. Some counties update daily; others update annually. Always check the "last updated" date on the data portal before relying on it for critical decisions.

Summary

Public parcel data is an invaluable resource. By leveraging ArcGIS REST services and browser-based downloaders, you can easily access and analyze property boundaries for any county in the US.