Zajączkowo was formerly part of the German Empire. In the German Empire, the place was called Falkenstein.
The place is now called Zajączkowo and belongs to Poland.
| Historical place name | Country | Administration | Time |
|---|---|---|---|
| Falkenstein | German Empire | Osterode i. Ostpr. | 1939 |
| Zajączkowo | Under Polish administration | Ostróda | 1945 |
| Zajączkowo | Poland | Olsztyn | 1992 |