Data caveats
Every limitation we know about, field by field. These are the same notes shown on each layer inside the atlas, published here so you can check them before deciding whether an indicator supports the claim you want to make.
Cross-cutting method and reconciliation notes are on the methodology page.
Population
An estimate for 1 July 2025, not a count. It starts from the 2020 Census and adds births, deaths and migration since; the next census will revise it.
Density
Population over land area only (the boundary files' ALAND). Lakes, bays and coastal water are left out, so a county that is mostly water is not made to look empty.
Missing is never zero. Where a source has no figure for a county, that county renders as no-data rather than as a zero value. If a map looks patchy, that's coverage being shown honestly, not a rendering fault.