Sielc Nowy was formerly part of the German Empire. In the German Empire, the place was called Sielz Neu.
The place is now called Sielc Nowy and belongs to Poland.
| Historical place name | Country | Administration | Time |
|---|---|---|---|
| Sielc Nowy | Russian Empire | Pultusk | 1914 |
| Sielc Nowy | Poland | Pułtusk | 1919 |
| Sielz Neu | German Empire | Mackeim | 1939 |
| Sielc Nowy | Poland | Maków Mazowiecki | 1945 |
| Sielc Nowy | Poland | Ostrołęka | 1992 |