The Treaty of Frankfurt gave the residents of the region until October 1, 1872 to choose between emigrating to France or remaining in the region and having their nationality legally changed to German. By 1876, about 100,000 or 5% of the residents of Alsace-Lorraine had emigrated to France.[3]

The "being French" feeling stayed strong at least during the first sixteen years of the annexation. During the Reichstag elections, the fifteen deputies of 1874, 1881, 1884 (but one) and 1887 were called protester deputies (fr: députés protestataires) because they expressed to the Parliament their opposition to the annexation by the mean of the 1874 motion in French language: « May it please the Reichstag to decide that the populations of Alsace-Lorraine that were annexed, without having been consulted, to the Germanic Empire by the treaty of Frankfurt have to come out particularly about this annexation[4]. »

Under the German Empire of 1871-1918, the territory constituted the Reichsland or Imperial Province of Elsass-Lothringen. The area was administered directly by the imperial government in Berlin and was granted some measure of autonomy in 1911. This included its own flag, and the Elsässisches Fahnenlied as anthem. The infamous Saverne Affair (1913) however showed that this status was of no high value in the eyes of the Berlin government.