Duchy of Parma
With the Treaty of Aix-la-Chapelle (1748), Guastalla was joined to the Duchy of Parma, ruled by the Spanish Bourbons. It was annexed to the Cisalpine Republic in 1802 but became an autonomous duchy in 1806. It was returned in 1815 to the Duchy of Parma, and it remained until 1847 under Parma's rule. With the death in 1847 of Marie Louise, Duchess of Parma, the duchy then passed to the Duchy of Modena and later on to the unified Kingdom of Italy.