Landgraviate of Hesse-Kassel
The varying lords made continued attempts to challenge Gelnhausen's imperial immediacy, it however formally remained a "Reichsstadt". During the German Mediatisation of 1803 the city became a part of the Landgraviate of Hesse-Kassel, which was raised to an electorate and, after the Austro-Prussian War of 1866, was annexed by Prussia. At this time Gelnhausen had completely recovered, and with the "Gründerzeit" economic boom it became a centre of the German rubber industry.