Northern Germany corresponds to the territory of the North German Confederation in the 19th century. The boundary between the spheres of political influence of Prussia (Northern Germany) and Austria (Southern Germany) within the German Confederation (1815–1866) was known as the "Main line" ("Mainlinie", after the River Main), Frankfurt am Main being the seat of the federal assembly. The "Main line" did not follow the course of the River Main upstream of Frankfurt, rather corresponding to the northern border of the Kingdom of Bavaria.