With the earliest extensions of the Roman territory coincided the first beginnings of the Roman road system. After the Latin communities on the lower Anio had fallen under the dominion of Rome, we may well believe that the first portion of the Via Salaria, leading to Antemnae, Fidenae and Crustumerium, came into existence. The formation of the tribus Clustumina (the only one of the earlier 21 tribes which bears a local name) is both a consequence of an extension of territory and of the establish ment of the assembly of the plebs by tribes, for which an in equality of the total number of divisions was desirable. The correlative of the Via Salaria was the Via Campana, so called because it led past the grove of the Arvales along the right bank of the Tiber to the Campus Salinarum Romanarum, the salt marshes, from which the Via Salaria took its name, inasmuch as it was the route by which Sabine traders came from the interior to fetch the salt, crossing the Tiber at Rome, just below the island. To this period would also belong the Via Ficulensis, lead ing to Ficulea, and afterwards prolonged to Nomentum, and the Via Collatina, which led to Collatia. Gabii became Roman in fairly early times, though at what period is uncertain, and with its subjugation must have originated the Via Gabina, afterwards prolonged to Praeneste. The Via Latina, too, must be of very early origin; and tradition places the important conquest of the pass of Algidus through which it led, in 431 B.C. Not long after the capture of Fidenae, the main outpost of Veii, the chief city itself fell (396 B.c.) and a road (still traceable) was probably made thither. The rival trade route from Veii to Fidenae (the Tiber being crossed by a ferry) Collatia, Gabii and Praeneste must then have fallen into desuetude. There was also probably a road to Caere in early times, inasmuch as we hear of the flight of the Vestals thither in 389 B.C. The origin of the rest of the roads is, no doubt, to be connected with the gradual establishment of the Latin league. We find that while the later (long distance) roads bear as a rule the name of their constructor, all the short distance roads on the left bank of the Tiber bear the names of towns which belonged to the league—Nomentum, Tibur, Prae neste, Labici, Ardea, Laurentum—while Ficulea and Collatia do not appear. The Via Pedana, leading to Pedum, may be of much later origin; it was a branch of the Via Praenestina.
There must, too, have been a road, along the line of the later Via Appia, to Bovillae, Aricia, Lanuvium and Velitrae, going thence to Cora, Norba and Setia along the foot of the Volscian mountains; while nameless roads, which can still be traced, led direct from Rome to Satricum and to Lavinium.
We can trace the advance of the Roman supremacy with greater ease after 387 B.C., inasmuch as from this year (adopting the traditional dating for what it is worth) until 299 B.C. every accession of territory is marked by the foundation of a group of new tribes ; the limit of 35 in all was reached in the latter year.
In 387, of ter the departure of the Gauls, southern Etruria was conquered, and four new tribes were formed : Arnensis (probably derived from Aro, mod. Arrone—the stream which forms the outlet to the lake of Bracciano, anc. Lacus Sabatinus), Sabatina
(called after this lake), Stellatina (named from the Campus Stellatinus, near Capena) ; and Tromentina. Four years later were founded the Latin colonies of Sutrium and Nepeta. In 358 B.C. Roman preponderance in the Pomptine territory was shown by the formation of the tribus Pomptina and Publilia, while in 338 and 329 respectively Antium (founded as a Latin colony in 494 B.c.) and Tarracina became colonies of Roman citizens.
After the dissolution of the Latin league which followed upon the defeat of the united forces of the Samnites and of those Latin and Volscian cities which had revolted against Rome, two new tribes, Maecia and Scaptia, were created in 332 B.C. in con nection with the distribution of the newly-acquired lands. A further advance in the same direction, ending in the capture of Privernum in 329 B.C., is marked by the establishment in 318 B.C. of the tribus Oufentina (from the river Ufens which runs below Setia, mod. Sezze, and Privernum, mod. Piperno, and the tribus Falerna (in the Ager Falernus), while the foundation of the colonies of Cales (334) and Fregellae (328) secured the newly won south Volscian and Campanian territories, and led no doubt to a prolongation of the Via Latina. The moment had now come for the pushing forward of another line of communication, which had no doubt reached Tarracina in 329 B.C. but was now definitely constructed (munita) as a permanent military highway as far as Capua in 312 B.C. by Appius Claudius, after whom it was named. To him, no doubt, is due the direct line of road through the Pomp tine marshes from Velitrae to Tarracina. Its construction may fairly be taken to mark the period at which the roads of which we have spoken, hitherto probably mere tracks, began to be trans formed into real highway.
In the same year (312) the colony of Interamna Lirenas was founded, while Luceria, Suessa (Aurunca) and Saticula had been established a year or two previously. Sora followed nine years later. In 299 B.C. further successes led to the establishment of two new tribes—the Teretina in the upper valley of the Trerus (Sacco) and the Aniensis, in the upper valley of the Anio—while to about the same time we must attribute the construction of two new military roads, both secured by fortresses. The southern road, the Via Valeria, led to Carsioli and Alba Fucens (founded as Latin colonies respectively in 298 and 3o3 B.c.), and the northern (afterwards the Via Flaminia) to Narnia (founded as a Latin colony in 299 B.c.). There is little doubt that the formation of the tribus Quirina (deriving its name possibly from the town of Cures) and the tribus V elina (from the river Velinus, which forms the well-known waterfalls near Terni) is to be connected with the construction of the latter high road, though its date is not certainly known. The further history of Roman supremacy in Italy will be found in the article ROME : History. We notice, however, that the continual warfare in which the Roman State was engaged led to the decadence of the free population of Latium, and that the extension of the empire of Rome was fatal to the prosperity of the territory adjoining the city.