During the last decade, several county definitions have changed due to mergers with another county, being dissolved and distributed into other counties, or undergoing a name change.
In the descriptions of the county changes below 'old' counties that no longer exist are italicized, while 'new' counties that are now included in the Rankings are bolded.
- Prince of Wales – Outer Ketchikan Census Area was dissolved and distributed into other counties including Ketchikan Gateway Borough, Prince of Wales-Hyder Census Area, and Wrangell City and Borough
- Skagway-Hoonah-Angoon Census Area was split into Hoonah-Angoon Census Area and Skagway Municipality
- Wrangell-Petersburg Census Area was split into Hoonah-Angoon Census Area, Petersburg Borough, and Skagway Municipality
- Wade Hampton Census Area was renamed Kusilvak Census Area
In South Dakota
- Shannon County was renamed Oglala Lakota County
- Bedford City was absorbed into Bedford County. The new Bedford County has the same name as when these counties were separate; however, measures over time may not be consistent since the county composition has changed.
These changes mean that data for these ‘old’ counties are no longer displayed on our website; therefore, if a county was ranked prior to 2017, there may appear to be a gap in ranks for that year on our website. However, data for these ‘old’ counties will continue to be available in the files available for download for the years these counties existed. For more detailed information on the county changes (and/or FIPS code changes) listed above, please see https://www.census.gov/geo/reference/county-changes.html.