Gaj was formerly part of the German Empire. In the German Empire, the place was called Gaj.
The place is now called Gaj and belongs to Poland.
| Historical place name | Country | Administration | Time |
|---|---|---|---|
| Gaj | Russian Empire | Pultusk | 1914 |
| Gaj | Poland | Pułtusk | 1919 |
| Gaj | German Empire | Ostenburg | 1939 |
| Gaj | Poland | Pułtusk | 1945 |
| Gaj | Poland | Ciechanów | 1992 |