In January 1771 the Perpetual Diet of Regensburg ratified Ferdinand's future investiture and, in October, Maria Beatrice and he finally got married in Milan, thus giving rise to the new House of Austria-Este.

Francis III ceded to the archduke the post of governor of Milan which he had assumed ad interim after the 1753 agreement and which was destined for the third male heir of the imperial couple.

In accordance with the 'principle of legitimacy' advocated by Metternich at the Congress of Vienna, Maria Beatrice was restored as sovereign of the 'Duchy of Massa and Principality of Carrara' in 1815, and the Imperial fiefs in Lunigiana, which had not been re-established, were also bestowed upon her.

With an agreement in December, however, she ceded them to her son Francis IV who had been installed on the throne of the Duchy of Modena and Reggio, as heir to his father Ferdinand, in turn held to be the legal successor of Ercole III.

On her death, in 1829, she too was succeeded as ruler of Massa and Carrara by Francis IV, who in a few years completely assimilated his mother's ancient Tuscan domains within the 'Este States' (Stati Estensi), as his Duchy was officially styled.