The tribe entered into the Roman alliance, retaining its own independence, in 302 BC, and issuing coins of its own in the following century. A northerly section round Amiternum near the passes into Sabine country probably received the Caerite franchise soon after. In spite of this, and of the influence of Hadria, a Latin colony founded about 290 BC (Livy, Epit. xi.), the local dialect, which belongs to the north Oscan group, survived certainly to the middle of the 2nd century BC (see the inscriptions cited below) and probably until the Social War.
The oldest Latin inscriptions of the district are C.I.L. ix. 3521, from Furfo with Sullan alphabet, and 3574, "litteris antiquissimis," but with couraverunt, a form which, as intermediate between coir- or coer- and cur-, cannot be earlier than 100 BC. The latter inscription contains also the forms magisterles (nom. p1.) and ueci (gen. sing.), which show that the Latin first spoken by the Vestini was not that of Rome, but that of their neighbours the Marsi and Aequi. The inscription of Scoppito shows that at the time at which it was written the upper Aternus valley must be counted Vestine, not Sabine in point of dialect.