250 years have passed since Don Giacomo Mossa arrived on the island of Maddalena. In 1773, he took over from Don Virgilio Mannu, parish priest of the very young community (founded in 1767) and of the equally very young parish of Santa Maria Maddalena (established in 1768). The parish priest Mossa (who was also the royal chaplain of the military garrison) remained on the island for 26 years, until 1799. That was an important period for the island community, recently annexed to the Savoyard state, years which saw the population go from the original 185 inhabitants in 1767 to over 800 at the end of the century, its progressive movement towards the sea, the consolidation of the military garrison with the construction of some fortresses, the building of the new parish church in Cala Gavetta, near the sea, after the one built on Colle Piano (currently SS. Trinità), the attempted occupation by the Franco-Corse revolutionary troops (1793) with Napoleon Bonaparte, the progressive transformation from an agro-pastoral economy to another based on fishing, on service on the Royal military ships, on small cabotage (and smuggling), on trade and other small activities that today we call tertiary.

We do not know how old Giacomo Mossa was when he arrived in Maddalena, nor where he was originally from. He was probably of mature age, and since the parish church is in the center of the island, on a plateau (where the church of the Holy Trinity is today), he initially had to live in those parts. However, it is certain that it was he who had to take note, a few years after his arrival, of the need to celebrate Mass not only in the church of Colle Piano where by now few inhabitants lived but also in the marine area of Cala Gavetta, where not only it was consolidating the military presence but also concentrating the population. It was he who, in 1782, celebrated Mass in the new church "alla marina" built more or less where the current one stands. It was he who asked and obtained, in 1793 from the bishop of Ampurias and Tempio, by now considering the importance assumed by the new church, the "promotion" of this to parish church with the title of Santa Maria Maddalena and the "downgrading" of the other, renamed of the "Holy Trinity".