Methodology

US Lookup combines public datasets into consistent place pages. Each page focuses on a single geography (ZIP, county, metro, state, or area code) and highlights a bounded set of indicators with clear source and vintage notes.

Last updated: January 20, 2026

Place Types and Boundaries

ZIP codes: ZIP pages use Census ZCTAs for mapping and overlap estimates. ZCTAs are approximations and do not perfectly match USPS delivery routes.
Counties and states: Boundaries follow U.S. Census Bureau geography (TIGER/Line) where applicable.
Metro areas: Metros follow OMB Core Based Statistical Areas (CBSAs). County membership is defined by OMB delineations.
Area codes: Area codes are telecom numbering regions. Coverage can cross city/county lines and may change over time (splits/overlays).

Native vs. Context Metrics

We try to show indicators at the place's native geography (for example, ZIP-level ACS estimates on ZIP pages). When a dataset does not publish at a given geography, we either omit that indicator for the page type or show it as broader-area context (such as a county or metro rollup) and label it accordingly.

Ranking Context

When shown, "top quartile" / "bottom quartile" labels refer to percentile buckets within a comparison set (for example, ZIPs within the same county). These are descriptive comparisons, not quality ratings.

Data Freshness

Each place page includes a compact "Data freshness" block listing key vintages (ACS year, CDC PLACES year, storms last event date, etc.).

For dataset links and notes, visit Sources.

Contact

Questions about methodology: data@uslookup.org.