|boundary = historic|
|A historic administrative boundary kept temporarily in OSM to avoid recreation|
|Used on these elements|
|Status: in use|
|Tools for this tag|
A historic administrative boundary. Subdivisions of areas/territories/jurisdictions recognised by governments or other organisations for administrative purposes.
Note that though historic objects should not be mapped as it is outside of scope of OSM (unlike projects like Open Historical Map), it makes sense to keep for some time old boundaries after administrative division change as form of note to make clear that there was a recent change of borders in a given location. Using this tag is alternative to using note=*.
See comparison of life cycle concepts for more possibilities.
Note that OpenStreetMap is not a correct place to map borders of historical entities like Nazi Germany, Roman Empire or Polish-Lithuanian Commonwealth that are not going to be mapped by people mistakenly thinking that these entities exist.
admin_level=1 to 10 may be used in adition to further clarify situation.