By Roman times, the Arsia, as it was called in Latin, constituted the border between the
Histri, who lived west of its banks, and the
Liburni on the coast to the east, with the
Iapydes in the upcountry valley behind them. After the Romans conquered the fierce and piratical Histri in 177 BC, the Arsia formed the
limes of Roman territory in coastal Istria for a generation, until the gap between the Arsia and the northernmost Roman outposts in Illyria was closed in 129; for long afterwards it divided
Italia and its
regio X, from
Illyricum, according to the divisions ratified by
Augustus. The 8th-century Irish monk and geographer
Dicuil, following his late Latin sources for the geographical summary
De mensura Orbis terrae, gives the northeastern boundary of Italia as
flumen Arsia. The
Roman road Via Flavia, reaching from Tergeste (Trieste) into Istria came to an end at the crossing of the Arsia; beyond, it continued into
Dalmatia as a local road that linked to
Via Gemina. In the early 10th century
Tomislav of Croatia ruled a state that ran from the Adriatic to the
Drava, and from the Raša, as it was now being called, to the
Drina. In the 13th century, the territory on the east bank was administered by the
counts of Gorizia, while that on the west was ruled by the
patriarchs of Aquileia. the Raša became the border between
Napoleon's Kingdom of Italy and the
Austrian Empire; following Napoleon's downfall, Austria gained all of Istria and the river became the border between two Austrian provinces. The planned city of
Raša (), on the tributary
Krapanski Potok of the river in the inner part of the Raška Inlet, was constructed in 1936–1937 as
Arsia on drained
wetlands to gain arable land for farming and to serve expanding coal mining operations, as part of Mussolini's urban colonization and Italianization of Istria. The village of
Barban is the other major settlement near the river. ==References==