The Republic of Mainz was the first democratic state in the current German territory and was centered in Mainz. A product of the French Revolutionary Wars, it lasted from March to July 1793. By order of the French National Convention, elections in the French-occupied territories west of the Rhine were held on 24 February 1793. 130 cities and towns sent their deputies to Mainz. The first democratically elected parliament on the territory of future Germany, called the Rheinisch-Deutscher Nationalkonvent (English: Rhenish-German National Convention), met initially on 17 March 1793, in the Deutschhaus building in Mainz (today the seat of the Rhineland-Palatinate state parliament). The convention declared the represented territory (which extended to Bingen in the west and to Landau in the south) to be free and democratic, and disclaimed any ties to the empire. The convention's president, Andreas Joseph Hofmann, proclaimed the Rhenish-German Free State (German: Rheinisch-Deutscher Freistaat) from the balcony of the Deutschhaus. On 21 March 1793, it was decided to seek the accession of the Free State to France and delegates (among them Georg Forster and Adam Lux) were sent to Paris. The French National Convention granted the request on 30 March.
Soon after, Prussian troops retook all the French-occupied territory except for the heavily fortified city of Mainz itself. After a long siege in which much of the city was destroyed, Prussian and Austrian troops conquered the city on 22 July 1793. The republic ended, and the Jacobins were persecuted until 1795 when Mainz came under French control again.

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https://en.wikipedia.org/wiki/Republic_of_Mainz