Ostaszewo was formerly part of the German Empire. In the German Empire, the place was called Buchenau.
The place is now called Buchnowo and belongs to Poland.
| Historical place name | Country | Administration | Time |
|---|---|---|---|
| Ostaszewo, Kr. Löbau i. Westpr. | German Empire | Löbau | before the Versailles Treaty |
| Buchenau | German Empire | Löbau | before the Versailles Treaty |
| Ostaszewo | Poland | Lubawa | after the Versailles Treaty |
| Buchnowo | Poland | Lubawa | after the Versailles Treaty |
| Stechau, Kr. Neumark (Westpr.) | German Empire | Neumark (Westpr.) | 1939 |
| Buchenau | German Empire | Neumark (Westpr.) | 1939 |
| Ostaszewo | Poland | Działdowo | 1945 |
| Buchnowo | Poland | Działdowo | 1945 |
| Ostaszewo | Poland | Toruń | 1992 |
| Buchnowo | Poland | Toruń | 1992 |