The Territoire de Belfort is a department located in eastern France, specifically in the
Bourgogne-Franche-Comté region. Interestingly, this department has a unique history that sets it apart from other administrative divisions in the country. The Territoire de Belfort was created as a distinct administrative district, with the number 90 assigned to it, as part of the Treaty of Frankfurt terms in 1871. This treaty was signed following the Franco-Prussian War, which ended with Germany's victory and the annexation of Alsace-Lorraine by the German Empire. Despite the annexation of almost the entire region of Alsace, the French were able to negotiate the retention of the Territoire de Belfort, which resulted in its separation from the rest of Alsace. As a result, this department became a unique territory recognised as such for over half a century.
It was only in 1922 that the Territoire de Belfort was designated France's 90th department. Interestingly, even though France had recovered the Alsace region three years earlier, the authorities decided to keep Belfort separated from its former department. This decision highlights the unique history and status of this department within France.