It was wanted by Pietro Leopoldo, the Grand Duke of Tuscany, in 1778 to control and manage the business traffic that went from the sea side to the internal part of the Granduchy. It was complitely built with bricks comeing from Torre Trappola kiln and it was comlpeted 1798. A few years later, a small settlement of fishermen began to develop around the fortification: that settlement is nowdays transformed in a quarter of the modern town called Shangai.
They say that there was a structure, not far from Forte San Rocco, dedicated to desease recovery and quarantine: maybe it was not more than a hut, but the choice of the name of the fortification is really connected to the activity of this hut. San Rocco, infact, is the Saint protector of deseased and sick people.