In this work, historian Brad Franco examines the legend of Montaperti, the story of the extraordinary events which preceded Siena’s victory over Florence in 1260, culminating in the donation of the keys of the city to the Virgin Mary. Is there any historical evidence that the donation ever occurred? If not, what explains the resurgence of interest in Montaperti and the key donation during the Renaissance? And why does the legend remain so important to the Sienese today? Through a careful analysis of the vast historiography on the topic and a consideration of the primary sources, Franco answers these questions and argues that, regardless of the historical reality, the legend is revealing about the values, beliefs, and ideals of the Sienese during the Renaissance.