Manasseh was 12 years old when he became king; he reigned 55 years in Jerusalem. His mother's name was Hephzibah.
2 Kings 21:1 In-Context
Manasseh was twelve years old when he became king, and he reigned in Jerusalem fifty-five years. His mother’s name was Hephzibah.
He did evil in the eyes of the LORD, following the detestable practices of the nations the LORD had driven out before the Israelites.
He rebuilt the high places his father Hezekiah had destroyed; he also erected altars to Baal and made an Asherah pole, as Ahab king of Israel had done. He bowed down to all the starry hosts and worshiped them.
He built altars in the temple of the LORD, of which the LORD had said, “In Jerusalem I will put my Name.”
In the two courts of the temple of the LORD, he built altars to all the starry hosts.