Geography & Mapping
The spatial side of postal codes — ZCTA boundaries, time zones, congressional districts, and the urban-rural divide.
ZCTA Boundaries: How the Census Maps ZIP Codes
ZIP codes have no official boundaries. The Census Bureau's ZCTAs create geographic approximations — here's how they are built.
Time Zones and ZIP Codes
Most ZIP codes fall in one time zone, but border ZIPs can span two — and some states complicate matters further.
Congressional Districts and ZIP Codes
ZIP codes and congressional districts overlap imperfectly. Understanding this relationship is crucial for civic engagement.
Urban, Suburban, and Rural: Classifying ZIP Codes
There is no single definition of 'urban' or 'rural.' Learn how the Census Bureau and USDA classify ZIP codes along the urban-rural spectrum.
Geocoding ZIP Codes: From Code to Coordinates
Converting ZIP codes to latitude/longitude is essential for mapping. Learn the methods, accuracy levels, and common pitfalls.
Counties, FIPS Codes, and ZIP Codes
ZIP codes and counties were drawn for different purposes and don't align. Learn about FIPS codes and cross-boundary mapping.
MSAs and CBSAs: Metro Area Definitions
Metropolitan statistical areas group counties around urban cores. Learn how MSAs and CBSAs relate to ZIP codes.
How ZIP Code Boundaries Cross State Lines
A handful of ZIP codes span two states, creating legal and administrative complications. Here are the edge cases.