Rumunek was formerly part of the German Empire. In the German Empire, the place was called Ulatowo Rumunek.
The place is now called Ulatowo-Rumunek and belongs to Poland.
| Historical place name | Country | Administration | Time |
|---|---|---|---|
| Rumunek | Russian Empire | Prasnyš | 1914 |
| Rumunek | Poland | Przasnysz | 1919 |
| Ulatowo Rumunek | German Empire | Praschnitz | 1939 |
| Ulatowo-Rumunek | Poland | Przasnysz | 1945 |
| Ulatowo-Rumunek | Poland | Ostrołęka | 1992 |