The beginning of the fifteenth century saw a period of crisis, due to new plagues and related famines. During the war between Florence and the Republic of Siena, Castiglione was taken by the Florentine (but an enemy of Cosimo I de 'Medici) Piero Strozzi, before returning to Florence in a short time (1554).
The Medici government followed that of the Grand Duchy of Lorraine (1765). It was above all Pietro Leopoldo who decided to re-evaluate the marsh area, entrusting the engineer Vittorio Fossombroni to reclaim it. In 1774 the same Pietro Leopoldo ordered an administrative reorganization of the Grand Duchy: the municipality of Castiglion Fiorentino were thus annexed those of Montecchio Vesponi, Mammi and della Montanina.
The Florentine dominion was interrupted in 1799, when the French took Tuscany. As in all the conquered cities, the tree of freedom was raised in Castiglion Fiorentino (in Piazza del Mercato, today's Piazzale Garibaldi). Except for a brief interval, during which the city was freed by the insurgents of the "Viva Maria", Castiglion Fiorentino was garrisoned by Napoleon's troops from 1800 to 1814. With the Restoration the Lorena returned, which completed the reclamation works of the Valdichiana.
Thursday, June 21, 1849, Garibaldi at noon coming from Cortona arrived in the town. He was head of about 4,000 veterans of the Roman Republic, who rested and refreshed at the Parterre, today Piazzale Garibaldi. After parleying and raising funds and provisions from the hesitant local authorities, on the afternoon of the same day they resumed their march for Arezzo. The event was remembered not only with the obelisk in the square but with the rhyme: "Giuseppe Garibaldi came here and waited, ate, took the money and went away" (FONTE WIKIPEDIA)