Mierzęcin was formerly part of the German Empire. In the German Empire, the place was called Merzen.
The place is now called Mierzęcin and belongs to Poland.
| Historical place name | Country | Administration | Time |
|---|---|---|---|
| Mierzecin | Russian Empire | Rypin | 1914 |
| Mierzęcin | Poland | Rypin | after the Versailles Treaty |
| Merzen | German Empire | Rippin (Westpr.) | 1939 |
| Mierzęcin | Poland | Sierpc | 1945 |
| Mierzęcin | Poland | Płock | 1992 |