Roman Iron Age
The history of Latvia between 0 AD and 399 AD
An important development in the so-called Roman Iron Age (1–400 AD) was the spread of knowledge about how to smelt and work iron. The peasant culture of the Baltic made remarkable progress. This can be partly explained by the very lively trade relations between the Baltic and centers of the Roman Empire, particularly with the Danube Basin. The Balts exported amber, which at that time was valued higher than gold, and expensive furs. In return they received Roman manufactured goods and coins. At this period the Eastern Balts began to split up into Lithuanians and Latvians, and the Finno-Ugrians into Finns and Estonians. The former began to cross the Finnish Gulf and settle down in present-day Finland.
The Roman Iron Age is remarkable because even at that time the Eastern border of the three Baltic peoples was almost identical with the later ethnic and political frontiers. Beyond this border at that time were very sparsely populated territories of Eastern Europe; this proves that these frontiers have not been established in a struggle with some other nation, but developed naturally, as the natural cultural boundaries of the Baltic nations and as the maximum reach of these civilizations.
Reference: Latvians.com