The Census Bureau's annual population estimates generally reflect geographic entities and their boundaries effective as of January 1 of the reference year of the estimate. Population estimates may also include corrections to the most recent decennial census as processed via the Count Question Resolution Program. Other updates, such as address or boundary corrections and geocoding improvements, are also reflected in the estimates.
The geographic change notes page provides documentation for selected geographic changes to counties, county subdivisions, and places that have been processed by the Census Bureau since the last decennial census. Changes effective as of January 1 and submitted by April 1 of a given year will generally be reflected in that year's vintage of population estimates. For more information, see the About Geographic Change Notes page.