Question: "What is the significance of Decapolis in the Bible?"
Answer: Decapolis (“Ten Cities”) was a region east and southeast of the Sea of Galilee, north of Perea, and belonging to the half-tribe of Manasseh. It was so named for the ten cities that lay within its borders. The names of those cities are not certain. Pliny lists them as Scythopolis, Philadelphia, Raphanae, Gadara, Hippos, Dios, Pella, Gerasa, Canatha, and Damascus. Josephus replaces Canatha with Otopos on his list. Of the ten cities, only one, the capital Scythopolis, lay west of the Jordan River. Jesus visited the region of Decapolis during His ministry. Matthew calls it “the region of the Gadarenes,” because Jesus was near Gadara, in Matthew 8:28.
The ten cities that formed Decapolis probably entered their league with each other about the time the Roman general Pompey defeated Syria in 65 BC. Residents of Decapolis answered directly to the Roman governor in Syria. The alliance of cities enjoyed independence to the extent of being able to mint their own coins.
During the time of Christ, the ten cities of Decapolis and the surrounding region were inhabited mostly by Gentiles, not Jews, and the area had a strong Greek influence. This fact probably accounts for the presence of a large herd of swine near Gadara when Jesus visited that region to heal the demon-possessed men (Matthew 8:30–33; Mark 5:1–17). Pigs were an unclean animal, and even touching them was forbidden by Jewish law. The Gentiles who owned the pigs obviously did not see Jewish law as binding on them. Such disregard of the law may also help explain why Jesus allowed the demons to enter the swine so that the whole herd died. As He rid the men of demons, He helped rid this particular region of Israel of unclean animals.
The cities of Decapolis were the site of some of Jesus’ miracles. Mark 7:31–37 records how Jesus healed a deaf and mute man there. Many people from the region of Decapolis followed Him (Matthew 4:25). In AD 69, when Jerusalem came under attack by Rome, the city of Pella, in southern Decapolis, proved to be a place of refuge for Christians who fled the coming siege.