On the Hainfeld Party Convention of 1888/1889, Jakob Reumann was designated first secretary of the newly founded Social Democratic Party, which then united social democrats of the whole multinational Austrian part of Austria-Hungary.
1918/1919 he was also a member of the Provisional National Council of German Austria (Provisorische Nationalversammlung für Deutschösterreich).
Reumann had to defend this decision at the Constitutional Court as he had granted building permission for the crematorium against the order of a federal minister from the Christian Social Party.
[1] In 1923, the Gemeinderat concluded on the first large housing programme to build 25,000 flats within five years.
On 13 November 1923 Jakob Reumann stepped down as mayor and was made honorary citizen of Vienna.