The modern Roman Catholic Diocese of Mainz was founded in 1802, within the territory of France and in 1814 its jurisdiction was extended over the territory of Hesse-Darmstadt.
The modern Roman Catholic Diocese of Mainz was founded in 1802 when Mainz lost its archdiocese status and became a mere diocese within the territory of France. In 1814 its jurisdiction was extended over the territory of Hesse-Darmstadt.