The Decapolis and its Cities
 
    (Enlarge) (PDF for Print) (Freely Distributed)

Map of the Cities of the Decapolis in Israel

The Decapolis was an alliance of ten cities, originally Palestinian. All but one (Scythopolis) were on the east side of the Jordan. In New Testament times these cities were most definitely Greek in character and under the protection of Rome (Governor of Syria). 

Mark 7:31 - And again, departing from the coasts of Tyre and Sidon, he came unto the sea of Galilee, through the midst of the coasts of Decapolis.

The Decapolis in the Bible Encyclopedia - ISBE

DECAPOLIS
de-kap'-o-lis (Dekapolis): The name given to the region occupied by a league of "ten cities" (Mt 4:25; Mk 5:20; 7:31), which Eusebius defines (in Onomastica) as "lying in the Peraea, round Hippos, Pella and Gadara." Such combinations of Greek cities arose as Rome assumed dominion in the East, to promote their common interests in trade and commerce, and for mutual protection against the peoples surrounding them. This particular league seems to have been constituted about the time of Pompey's campaign in Syria, 65 BC, by which several cities in Decapolis dated their eras. They were independent of the local tetrarchy, and answerable directly to the governor of Syria. They enjoyed the rights of association and asylum; they struck their own coinage, paid imperial taxes and were liable to military service (Ant., XIV, iv, 4; BJ, I, vii, 7; II, xviii, 3; III, ix, 7; Vita, 65, 74). Of the ten cities, Scythopolis, the ancient Bethshean, alone, the capital of the league, was on the West side of Jordan. The names given by Pliny (NH, v.18) are Scythopolis (Beisan), Hippos (Susiyeh), Gadara (Umm Qeis), Pella (Fahil), Philadelphia (`Amman), Gerasa (Jerash), Dion (Adun?), Canatha (Qanawat), Damascus and Raphana. The last named is not identified, and Dion is uncertain. Other cities joined the league, and Ptolemy, who omits Raphans, gives a list of 18. The Greek inhabitants were never on good terms with the Jews; and the herd of swine (Mk 5:11 ff) indicates contempt for what was probably regarded as Jewish prejudice. The ruins still seen at Gadara, but especially at Kanawat (see KENATH) and Jerash, of temples, theaters and other public buildings, attest the splendor of these cities in their day.  Full Article

Decapolis in Easton's Bible Dictionary

Decapoils
        ten cities=deka, ten, and polis, a city, a district on the east
        and south-east of the Sea of Galilee containing "ten cities,"
        which were chiefly inhabited by Greeks. It included a portion of
        Bashan and Gilead, and is mentioned three times in the New
        Testament (Matt. 4:25; Mark 5:20; 7:31). These cities were
        Scythopolis, i.e., "city of the Scythians", (ancient Bethshean,
        the only one of the ten cities on the west of Jordan), Hippos,
        Gadara, Pella (to which the Christians fled just before the
        destruction of Jerusalem), Philadelphia (ancient Rabbath-ammon),
        Gerasa, Dion, Canatha, Raphana, and Damascus. When the Romans
        conquered Syria (B.C. 65) they rebuilt, and endowed with certain
        privileges, these "ten cities," and the province connected with
        them they called "Decapolis."  Full Article

The Bible Mentions the "Decapolis"

Mark 7:31 - And again, departing from the coasts of Tyre and Sidon, he came unto the sea of Galilee, through the midst of the coasts of Decapolis.

Matthew 4:25 - And there followed him great multitudes of people from Galilee, and [from] Decapolis, and [from] Jerusalem, and [from] Judaea, and [from] beyond Jordan.

Mark 5:20 - And he departed, and began to publish in Decapolis how great things Jesus had done for him: and all [men] did marvel.