The Rhine Province (green) as of 1830 superimposed on modern borders.
Historically, the Rhinelands refers (physically speaking) to a loosely defined region embracing the land on the banks of the Rhine in Central Europe, which were settled by Ripuarian and Salian Franks and became part of Frankish Austrasia. In the High Middle Ages, numerous Imperial States along the river emerged from the former stem duchy of Lotharingia, without developing any common political or cultural identity.
A "Rhineland" conceptualization did not evolve until the 19th century after the War of the First Coalition, when a short-lived Cisrhenian Republic was established by Napoleon. The term covered the whole French conquered territory west of the Rhine (German: Linkes Rheinufer), but also including a small portion of the bridgeheads on the eastern banks. After the collapse of the French empire, the regions of Jülich-Cleves-Berg and Lower Rhine were annexed to the Kingdom of Prussia. In 1822 the Prussian administration reorganized the territory as the Rhine Province (Rheinprovinz, also known as Rhenish Prussia), a tradition that continued in the naming of the current German states of Rhineland-Palatinate and North Rhine-Westphalia.
Following the First World War, the western part of Rhineland was occupied by Entente forces, then demilitarized under the 1919 Treaty of Versailles and then the 1925 Locarno Treaties. German forces remilitarized the territory in 1936, as part of a diplomatic test of will, three years before the outbreak of the Second World War.