Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
From: The History of Rome, by Theodor Mommsen
Translated with the sanction of the author by William Purdie Dickson
Here settled the stock which is known to history under the name of the Latins, or, as they were subsequently called by way of distinction from the Latin communities beyond the bounds of Latium, the "Old Latins" (-prisci Latini-). But the territory occupied by them, the district of Latium, was only a small portion of the central plain of Italy. All the country north of the Tiber was to the Latins a foreign and even hostile domain, with whose inhabitants no lasting alliance, no public peace, was possible, and such armistices as were concluded appear always to have been for a limited period. The Tiber formed the northern boundary from early times; and neither in history nor in the more reliable traditions has any reminiscence been preserved as to the period or occasion of the establishment of a frontier line so important in its results.
We find, at the time when our history begins, the flat and marshy tracts to the south of the Alban range in the hands of Umbro-Sabellian stocks, the Rutuli and Volsci; Ardea and Velitrae are no longer in the number of originally Latin towns. Only the central portion of that region between the Tiber, the spurs of the Apennines, the Alban Mount, and the sea--a district of about 700 square miles, not much larger than the present canton of Zurich--was Latium proper, the "plain," (2) as it appears to the eye of the observer from the heights of Monte Cavo. Though the country is a plain, it is not monotonously flat. With the exception of the sea-beach which is sandy and formed in part by the accumulations of the Tiber, the level is everywhere broken by hills of tufa moderate in height though often somewhat steep, and by deep fissures of the ground.
2. Like -latus- (side) and --platus-- (flat); it denotes therefore the flat country in contrast to the Sabine mountain-land, just as Campania, the "plain," forms the contrast to Samnium. Latus, formerly -stlatus-, has no connection with Latium.
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Reference address : https://www.ellopos.net/elpenor/rome/1-03-settlements-latins.asp?pg=5