Look up the correct State Plane Coordinate System zone and EPSG code for a county

Steps

1. Go to the NGS State Plane Coordinate System (SPCS) tools page at ngs.noaa.gov/SPCS/ (or geodesy.noaa.gov/SPCS/) to review the official zone maps and definitions maintained by NGS, the authoritative source for SPCS.
2. Identify which SPCS zone the county falls in using the NGS zone map for that state — some states have a single zone, others have multiple zones split by county groupings, so confirm your specific county's assignment rather than assuming a statewide zone.
3. Cross-reference the identified zone to its EPSG code using a spatial-reference registry (e.g., epsg.io or spatialreference.org) or your GIS/CAD software's built-in coordinate system library, and note there are typically separate EPSG codes for NAD 83 (various realizations) in feet vs. meters for the same zone.
4. Confirm which NAD 83 realization/epoch your project control is tied to, since the EPSG code differs by realization, and using the wrong one silently introduces a coordinate shift.
5. Document the chosen SPCS zone, EPSG code, and units (US survey feet, international feet, or meters — this varies by state) explicitly in the project metadata and on delivered plats.