Early history

After the dissolution of the Western Roman Empire, the area of the province of Trieste was ruled by the Ostrogoths, Eastern Romans (Byzantines), Lombards and by the Franks. With the advent of the Habsburgs (13th century) the territory was divided between the lords of Duino, Trieste, San Dorligo della Valle and Muggia. During the reign of Maria Theresa of Austria and, subsequently, Joseph II, the maritime trades were increased with institution of the free port.

In 1809, the area was ceded to France after the defeat of Austria in that year. After the French definitive defeat, the communes of Duino, Aurisina, Sgonico and Monrupino, which used to be part of Carniola, were annexed to that of Gorizia and Gradisca, while Trieste became a direct city of the Austrian Empire. San Dorligo della Valle and Muggia became part of Istria.

World War I left the territory of the province almost untouched, although fierce battles were fought just on its north-westernmost edges.

The whole area was occupied by Italy in November 1918, in the aftermath of Austria's defeat in World War I. It was officially annexed to Italy with the treaty of Rapallo of 1920, which also assigned all of the former Austrian Littoral to Italy.

Establishment

The Province of Trieste was first established in 1920. It comprised the territory of the province at the time of its abolition, as well as significant portions of the Karst Plateau and the region of Inner Carniola in present-day Slovenia. Between 1923 and 1943, the province of Trieste included also the communes of Monfalcone, Staranzano, Ronchi dei Legionari, San Canzian d'Isonzo, Turriaco, San Pier d'Isonzo, Fogliano Redipuglia and Grado (today in province of Gorizia), the current Slovenian municipalities of Sežana (including former communes of Dutovlje, Tomaj and Lokev), Divača (including former communes of Senožeče and Vremski Britof), Postojna (shortly Postumia before 1945; including former communes of Bukovje, Hrenovice and Slavina) and Pivka (including former communes of Šmihel and Košana), as well as some settlements in the present-day Slovenian municipality of Koper, namely Hrvatini, Elerji, Spodnje Škofije, Plavje and Osp.

After World War II

After the end of World War II, the Free Territory of Trieste was established as a free state on 15 September 1947. On 26 October 1954, Italy and Yugoslavia came to an understanding whereby the territory de facto was divided between the two states. Zone A of the free state became the new Province of Trieste and Zone B was to be administered by Yugoslavia. The Province of Trieste formally became a part of Italy on 11 October 1977, by the Treaty of Osimo.

The province was abolished on 30 September 2017.^[4] Two years later, it was restored in the form of a regional decentralization entity.^[3]