Dataset release catalog
A reference date identifies when a population is measured. A source vintage and publication snapshot identify which version of that observation you are using.
pep-2025-r1: initial annual publication
Published on this website September 30, 2026. Source: Census PEP Vintage 2025, July 1 observations for 2020–2025, with January 1, 2025 boundaries. National/state, county and place source files were released in different months of 2026.
census-history-r1: separate historical collection
Nation/state/DC census counts for 1910–2020, from the Census table published April 26, 2021. Retained September 30, 2026 and packaged with the initial download bundle; historical geographic definitions remain distinct from PEP 2025 boundaries.
Four dates to keep separate
The observation date is the July 1 reference date of an annual population estimate, or the census date for a count. The source publication date identifies when the producing agency released the table or file. Retrieval records when this publication obtained the exact source bytes. The website snapshot date identifies when the reviewed transformation was assembled.
A newer website update date does not make an observation a newer population measurement. Likewise, a revised estimate for a past date is not population growth between two dates. Keep the source vintage and geographic definition with a number when comparing publications.
Immutable archives and updates
The initial release is available through versioned CSV, JSON, raw-file, documentation and checksum downloads. Future approved vintages receive a new snapshot ID. A substantive website correction also receives a distinct publication version. Older files remain tied to their original identifiers rather than being silently rewritten.
The comparison tool pins the source snapshot, geographic IDs, interval and chart mode in a shareable URL. The launch has one annual vintage, so no multi-vintage revision chart is currently offered. Review selection and calculation methods, correction procedures and module coverage before combining releases.