The Medici family acquired its fortune through the success of its bold banking entrepreneurship. In the fifteenth century, thanks to Cosimo the Elder (1389-1464) and - above all - Lorenzo the Magnificent (1449-1492), the Medici consolidated their power, taking over the Signoria [municipal government] of Florence. After the republican interval, Tuscany became a Duchy (1531). The first Duke was Alessandro de' Medici (1510-1537). He was succeeded at his death by Cosimo (1519-1574) , who, in 1569, assumed the title of Grand Duke under the name Cosimo I. The family continued to rule Tuscany until the death of Gian Gastone (1671-1737), when, in the absence of direct heirs, the Grand Duchy of Tuscany passed to the Lorraine family.