Harknag was formerly part of the German Empire. In the German Empire, the place was called Harknag.
The place is now called Harknag and belongs to Denmark.
| Historical place name | Country | Administration | Time |
|---|---|---|---|
| Harknag | German Empire | Tondern | before the Versailles Treaty |
| Harknag | Denmark | Tønder | after the Versailles Treaty |
| Harknag | Denmark | Sønderjylland | 1993 |