Herod was assigned a territorial rulership by the Romans, making him a "client king." His area covered from Gaza to Masada in southern Israel, north beyond Nazareth, and then a section east beyond the Golan Heights into what is today Syria. If Herod had not died while Jesus was still an infant, he certainly would have been a problem later because this is the very area that Christ lived and conducted His entire recorded ministry.
The House of Herod was a player in some other events in ancient history. Herod's father had given crucial help to Julius Caesar when he was down in Egypt, cut off from his supplies, and Caesar rewarded him handsomely for that. Herod himself shrewdly advised his friend Mark Antony to drop Cleopatra and make peace with Rome (advice he should have followed). And once Augustus emerged victorious from the civil wars, he was so impressed with young Herod that he allowed him to become one of his most trusted friends.
Of Jewish heritage Herod undertook substantial construction projects yet was nevertheless disliked by his subjects. He was considered a tyrant, taxed his subjects heavily and his allegiances seemed to rest with Rome. Herod is believed to have died at his Winter Palace in Jericho around 4 B.C., not very long (perhaps not more than a year) after Joseph and Mary fled with Jesus into Egypt.