Ur was the land of Haran’s nativity (Genesis 11:28), the place from which Terah and Abraham started “to go into the land of Canaan” (Genesis 11:31). It is called in Genesis “Ur of the Chaldaeans,” while in the Acts Stephen places it, by implication, in Mesopotamia (Acts 7:2, 4). These are all the indications which scripture furnishes as to its locality. It has been identified by the most ancient traditions with the city of Orfah in the highlands of Mesopotamia, which unite the table-land of Armenia to the valley of the Euphrates. In later ages it was called Edessa and was celebrated as the capital of Abgarus or Acbarus, who was said to have received the letter and portrait of our Saviour. “Two physical features must have secured Orfah, from the earliest times, as a nucleus for the civilization of those regions. One is a high-crested crag, the natural fortifications of the crested citadel. … The other is an abundant spring, issuing in a pool of transparent clearness, and embosomed in a mass of luxuriant verdure, which, amidst the dull brown desert all around, makes and must always have made, this spot an oasis, a paradise, in the Chaldaean wilderness. Round this sacred pool, ‘the beautiful spring Callirrhoe,’ as it was called by the Greek writers, gather the modern traditions of the patriarch.”—Stanley, Jewish Church, part i.p.7. A second tradition, which appears in the Talmud, finds Ur in Warka, 120 miles southeast from Babylon and four east of the Euphrates. It was the Orchoe of the Greeks and probably the Ereck of Holy Scripture. This place bears the name of Huruk in the native inscriptions and was in the countries known to the Jews as the land of the Chaldaeans. But in opposition to the most ancient traditions, many modern writers have fixed the site of Ur at a very different position, viz. in the extreme south of Chaldaea, at Mugheir, not very far above—and probably in the time of Abraham actually upon—the head of the Persian Gulf. Among the ruins which are now seen at the spot are the remains of one of the great temples, of a model similar to that of Babel, dedicated to the moon, to whom the city was sacred (Porter and Rawlinson favor this last place).
Smith's Bible Names Dictionary (1866)