The name of the Rhaetians is first mentioned by Polybius, but merely incidentally, and they played no part in Roman history till after the fall of the republic. It is certain, however, that they continued virtually independent until Augustus undertook their subjugation, in common with that of the neighbouring Alpine tribes bordering upon Italy. The importance he attached to this task is shown by his having deputed its execution to his two step-sons, Drusus and Tiberius, who in a single campaign reduced them all to subjection (15 b.c. ), so that their territory was shortly after incorporated as a province in the Roman empire and their name never again appears in history. The exploits of the imperial youths on this occasion have been immortalized in two well-known odes of Horace (Od., iv. 4 and 14). In the time of Strabo their territory was considered as extending from the Lakes of Como and Garda to that of Constance (the Lacus Brigantinus), while the allied people of the Vindelici, who had shared in their contest against the Roman arms, as well as in their final subjugation, extended down the northern slope of the Alps as far as the Danube. By far the greater part of this extensive region was occupied by rugged mountains, the inhabitants of which, when compelled to abandon their predatory habits, subsisted principally upon the produce of their flocks. Some of the valleys, however, which extended on the south side down to the plains of Italy, were rich and fertile, and produced excellent wine, which was considered equal to any of those grown in Italy itself. The most important of these valleys λvas that of the Adige, which descends from the high Alps adjoining the Brenner to Verona; of this the upper portions were held by the Breuni, whose name is still perpetuated in that of the Brenner, while the lower and more fertile region was occupied by the Tridentini, whose chief town of Tridentum was the same as the now celebrated city of Trent. The next people towards the west were the Triumpilini, in the valley still known as Val Trompia; the Camuni in Val Camonica; the Orobii, who appear to have occupied the Val Tellina and adjoining districts; and the Lepontii, between the Lago Maggiore and the Pennine Alps. The tribes in the interior and heart of the mountain ranges cannot be for the most part assigned to definite localities. The Genauni, mentioned by Horace as well as by Strabo, are supposed to have occupied the Val di Non, and the Vennones or Venostes the lofty ranges near the source of the Adige.

The boundaries of the Roman province were repeatedly changed. At first it appears to have comprised all Vinde-licia, so as to have extended to the Danube from its sources to its confluence with the Inn, which constituted its eastern boundary on the side of Noricum. But at a later period this northern tract was separated from the central mountain region, and the two were named Rhaetia Prima and Rhaetia Secunda, in which form they appear in the Notitia. At the same time the southern valleys were gradually incorporated with Italy and assigned to the territory of the neighbouring municipal towns. Thus Tridentum, which was originally a Rhaetian town, came to be included in Venetia, and is ass.igned by Pliny to the tenth region of Italy. The only important town in the northern part of the province was the Roman colony of Augusta Vindelicorum, which still retains the name of Augsburg. The same is the case with Curia, now Chur or Coire, the capital of the Grisons, and Brigantia (Bregenz), which gave name in ancient times to the lake now called the Lake of Constance.

The province of Rhaetia was traversed by two great lines of Roman roads,—the one leading from Verona and Tridentum (Trent) across the pass of the Brenner to Innsbruck (Pons Oeni), and thence to Augsburg (Augusta Vindelicorum), and the other from Bregenz on the Lake of Constance, by Coire and Chiavenna, to Como and Milan.