Klasak Duzy was formerly part of the German Empire. In the German Empire, the place was called Groß Klasak.
The place is now called Klasak Duży and belongs to Poland.
| Historical place name | Country | Administration | Time |
|---|---|---|---|
| Klasak Duzy | Russian Empire | Veljunˈ | 1914 |
| Klasak Duży | Poland | Wieluń | 1921 |
| Groß Klasak | German Empire | Welungen | 1939 |
| Klasak Duży | Poland | Wieluń | 1945 |
| Klasak Duży | Poland | Sieradz | 1992 |