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
Settlements of the Etruscans in Italy
It is, on the other hand, a matter of historical interest to determine what were the oldest traceable abodes of the Etruscans, and what were their further movements when they issued thence. Various circumstances attest that before the great Celtic invasion they dwelt in the district to the north of the Po, being conterminous on the east along the Adige with the Veneti of Illyrian (Albanian?) descent, on the west with the Ligurians.
This is proved in particular by the already-mentioned rugged Etruscan dialect, which was still spoken in the time of Livy by the inhabitants of the Raetian Alps, and by the fact that Mantua remained Tuscan down to a late period. To the south of the Po and at the mouths of that river Etruscans and Umbrians were mingled, the former as the dominant, the latter as the older race, which had founded the old commercial towns of Atria and Spina, while the Tuscans appear to have been the founders of Felsina (Bologna) and Ravenna.
A long time elapsed ere the Celts crossed the Po; hence the Etruscans and Umbrians left deeper traces of their existence on the right bank of the river than they had done on the left, which they had to abandon at an early period. All the regions, however, to the north of the Apennines passed too rapidly out of the hands of one nation into those of another to permit the formation of any continuous national development there.
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Reference address : https://www.ellopos.net/elpenor/rome/1-09-etruscans.asp?pg=8