Albert Barnes Commentary Matthew 4:25

"And there followed him great multitudes from Galilee and Decapolis and Jerusalem and Judaea and [from] beyond the Jordan." — Matthew 4:25 (ASV)

From Decapolis. Decapolis was the name of a region within the territory of the half-tribe of Manasseh, primarily east of the Jordan. It received this name because it included ten cities—which is the meaning of the word Decapolis in Greek.

Geographers generally agree that Scythopolis was the chief of these cities and the only one of them west of the Jordan. They also generally agree that Hippo (Hippos), Gedara, Dion (or Dios), Pelea (or Pella), Gerasa (or Gergesa), Philadelphia, and Raphana (or Raphanae) were seven of the remaining nine cities; the other two were either Kanatha and Capitolias, or Damascus and Otopos.

These cities were inhabited chiefly by foreigners (Greeks), not by Jews, during the time of our Savior.

This explains the keeping of swine by the Gergesenes (Matthew 8:30–33), which was forbidden by Jewish law.