Zalszyn was formerly part of the German Empire. In the German Empire, the place was called Grothenberg.
The place is now called Załszyn and belongs to Poland.
| Historical place name | Country | Administration | Time |
|---|---|---|---|
| Zalszyn | Russian Empire | Serpec | 1914 |
| Załszyn | Poland | Sierpc | 1919 |
| Grothenberg | German Empire | Sichelberg | 1939 |
| Załszyn | Poland | Sierpc | 1945 |
| Załszyn | Poland | Płock | 1992 |