Gelnhausen was founded by Emperor Frederick Barbarossa in 1170, it is therefore nicknamed "Barbarossastadt". The place was chosen because it was at the intersection of the Via Regia imperial road between Frankfurt and Leipzig and several other major trade routes. Frederick had three villages connected by streets and surrounded by a wall. At the same time Gelnhausen received town privileges and a Kaiserpfalz was erected on an island of the Kinzig river. The emperor also granted trade privileges like the staple right which forced traveling merchants to offer their goods in the town for three days.
Hence Gelnhausen initially was a thriving trade city and head of a league of 16 towns of the Wetterau region. However prosperity came to an end already in 1326 when Emperor Louis IV gave the town in pawn to the counts of Hanau, redeemed shortly afterwards. In 1349 Count G�nther von Schwarzburg received Gelnhausen from Emperor Charles IV for renouncing his claims as elected King of the Romans, in condominium with the counts of Hohnstein, who sold their share to Schwarzburg in 1431. Schwarzburg was acquired in 1435 by Elector Palatine Louis III and the Hanau, since raised to a county.
Continued plundering in the Thirty Years' War as depicted by Hans Jakob Christoffel von Grimmelshausen in his novel Simplicius Simplicissimus made it nearly uninhabitable. In 1736, the extinction of the comital line of Hanau meant the condominium share was inherited by the Landgraviate of Hesse-Kassel, who acquired the Palatinate's share ten years later.
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 Gr�nderzeit economic boom became
