Stoupa was known in ancient times as Lefktra and this name survives as Lefktron, the village immediately behind Stoupa. Pausanias called here on his travels and recorded that "There is a stone statue of Asklepios and elsewhere of Ino. There is also a shrine and statue of Priam´s daughter Kassandra, locally called Alexandra; and there are wooden idols of Karneian Apollo exactly according to the traditions of the Lakonians of Sparta.

On the Acropolis is a sanctuary of Athena with a statue and there are a shrine and sacred grove of Eros at Lefktra“. The acropolis is now called the Kastro (castle) after the fortress built there by William de Villehardouin in 1252 following the conquest of the Peloponnese by the Franks. It was called Beaufort but very little remains to be seen except for a few walls and the remains of a tower on the summit. The castle was also called "Yisterna" which means cistern and there is a large cistern on the summit. The Museum in Kalamata displays a small, carved marble head of Athena which was found here.

From this time on, the History of Stoupa parallels that of the rest of Exo Mani. There are very few old houses in Stoupa but that is not surprising because of attacks by the Turks and pirates, nobody would have lived so close to the sea shore and they would have concentrated further inland at Lefktron where there used to be some tower houses. Stoupa itself would not have developed until after the Greek War of Independence when it would be deemed safer to live on the shore and even now it is little more than a village because the population during the winter is very small compared to summer.