The Duchy of Ferrara (Latin: Ducatus Ferrariensis; Italian: Ducato di Ferrara; Emilian: Ducà ad Frara) was a state in what is now northern Italy. It consisted of about 1,100 km2 south of the lower Po River, stretching to the valley of the lower Reno River, including the city of Ferrara. The territory that was part of the Duchy was ruled by the House of Este from 1146 to 1597. Borso d'Este, already Duke of Modena and Reggio, and lord of Ferrara, was raised to Duke of Ferrara by Pope Paul II. Borso and his successors ruled Ferrara as a quasi-sovereign state until 1597, when it came under direct papal rule. Source: Wikipedia (en)