The Duchy of Amalfi or the Republic of Amalfi was a de facto independent state centered on the Southern Italian city of Amalfi during the 10th and 11th centuries. The city and its territory were originally part of the larger ducatus Neapolitanus, governed by a patrician, but it extracted itself from Byzantine vassalage and first elected a duke in 958. During the 10th and 11th centuries Amalfi was estimated to have a population of 50,000–70,000 people. It rose to become an economic powerhouse, a commercial center whose merchants dominated Mediterranean and Italian trade in IX and X century, before being surpassed and superseded by the other maritime republics of the North, like Pisa, Venice, and Genoa. In 1073, Amalfi lost its independence, falling to Norman invasion and subsequently to Pisa in 1137.