Monte Argentario was probably an island in origin, that was connected afterward to the Tyrrenian coast by the thin Feniglia and Giannella's tombolos. The promontory was first inhabited in pre-historical ages, as we can see from the archeological remains founded in the Grotta degli Stretti and in Grotta di Cala dei Santi.
Strabone ( 24 D.C. ) in his writing "De Geographia", gives the first information about this area when he writes about the "Portus cosanus", place who is recalled again in the "Intera Provinciarum " (152 D.C.) where it is clear its connections to the etruscan town of Cosa.
During the Middle Ages Monte Argentario belonged to the Three Fountains' Abbey that execised its jurisdiction up to the XII-th century. From the XII-th century to the XIV-th century the village of Monte Argentario was first under the Aldobrandeschi's domination, then under the Orsini's family and in the end it passed to the Republic of Siena that started the fortification of the village, but it is thanks to the Spanish rule that the promontory became the most important strong hold in all Tuscany.
The two main villages on Monte Argentario are Porto Santo Stefano, facing west, and Porto Ercole facing east.
The Church of Sant'Erasmo, were the Spanish governors were buried, the Convento della Presentazione al Tempio, on the northern point of the Argentario mount, and the Noviziato di San Giuseppe worth a visit.
The Governor's Palace, Spanish governors' residence in Renaissance style, is located in the historic centre of Porto Ercole, while the Polveriera di Monte Argentario (Powder magazine of Monte Argentario), built between 1783 and 1784, rises on the summity of the Poggio della Polveriera.