Until 1871, Alsace included the area now known as the Territoire de Belfort, which formed its southernmost part. From 1982 to 2016, Alsace was the smallest administrative "région" in metropolitan France, consisting of the Bas-Rhin and Haut-Rhin departments. Territorial reform passed by the French Parliament in 2014 resulted in the merger of the Alsace administrative region with Champagne-Ardenne and Lorraine to form Grand Est. On 1 January 2021, the departments of Bas-Rhin and Haut-Rhin merged into the new European Collectivity of Alsace but remained part of the region Grand Est.