The UPR became the dominant party in Alsace during the Interwar era.
Founded in 1919, the UPR attracted most of the Alsatian adherents of the Catholic Centre Party in Alsace-Lorraine, formed since the mid-1890s, forming with 31% of the seats the strongest party in the Landtag of the former Alsace-Lorraine.
During the 1920s its members had largely sat in parliament among the Republican Federation group.
Considering this to have grown too right-wing, French-nationalist and centralist, they set up their own parliamentary group: the Republicans of the Centre (1932 to 1936) and the Independents of Popular Action (1936 to 1940).
The UPR, URL, and PDP merged in 1946 to the create the Popular Republican Movement (MRP).