Previously, the Greek historian Strabo wrote of Phoenicians sailing to the area in the 8th century BC whose oracle told them to build a temple for Hercules.

Historically, between the legend and Biblical references to Tarshish in the Book of Kings, Tartessos had come under Greek influence in the mid-seventh century BC.

[4] Archaeological investigation of the island has uncovered Roman installations related to fishing and sea salt production, as well as the remains of the city of Salthish, an eleventh-century Muslim settlement, part of the Taifa of Saltés and Huelva.

The population was devoted to metallurgy and the metal trades, taking advantage of the site's proximity to the northern mines whose minerals came to the city by the river now known as Rio Tinto.

Although it had an official maximum capacity of less than 2,000, oral testimonies raise the number of inmates to more than 5,000; in fact, by March 1939 3,197 prisoners were crowded in awful conditions inside the camp, which remained open at least between February and September 1939.