In 49 BC, perhaps on the 10th January, Julius Caesar led a single legion, Legio XIII Gemina, south over the Rubicon from Cisalpine Gaul to Italy to make his way to Rome.

According to Suetonius, Caesar uttered the famous phrase alea iacta est ('the die is cast') upon crossing the Rubicon, signifying that his action was irreversible.

After Caesar's crossing, the Rubicon was a geographical feature of note until about 42 BC, when Octavian merged the Province of Cisalpine Gaul into Italia and the river ceased to be the extreme northern border of Italy.

For this reason, and to supply fields with water after the revival of agriculture in the late Middle Ages, during the 14th and 15th centuries, hydraulic works were built to prevent other floods and to regulate streams.

With the revival during the fifteenth century of interest in the topography of ancient Roman Italy, the matter of identifying the Rubicon in the contemporary landscape became a topic of debate among Renaissance humanists.

In a section of the Tabula Peutingeriana, a medieval copy of a Late Antique document showing the network of Roman roads, a river in northeastern Italy labeled "fl.

Strong evidence supporting this theory came in 1991,[7] when three Italian scholars (Pignotti, Ravagli, and Donati), after a comparison between the Tabula Peutingeriana and other ancient sources (including Cicero), showed that the distance from Rome to the Rubicon River was 200 Roman miles.