In antiquity, the Achelous was the largest and most celebrated river in Greece, rising in Mount Pindus, and after flowing through the mountainous country of the Dolopians and Agraeans, entered the plain of Acarnania and Aetolia near Stratus, and discharged itself into the Ionian Sea, near the Acarnanian town of Oeniadae. It subsequently formed the boundary between Acarnania and Aetolia, but in the time of Thucydides the territory of Oeniadae extended east of the river. It is usually called a river of Acarnania, but it is sometimes assigned to Aetolia. Its general direction is from north to south. Its waters are of a whitish yellow or cream colour, whence it derives a later name of "Aspropotamo" or the White river, and to which Dionysius Periegetes probably alludes in the epithet ἀργυροδίνης. Periegetes places the sources of the river near a place called Chalcis. It is said to have been called more anciently Thoas, Axenus and Thestius. In the lower part of its course, the plain through which it flows was called in antiquity Paracheloitis after the river. This plain was celebrated for its fertility, though covered in great part with marshes, several of which were formed by the overflowings of the Achelous.