Go back and read 1 Kings 12. Rehoboam was the son of Solomon and succeeded him as king. Aganist sound advice, he foolishly chose to tax the people heavily and to rule with an iron fist. When he chose this course, one of Solomon’s old enemies, Jeroboam, rose up and led most of the tribes to set up a new nation. Thus we had the southern kingdom of Judah, under Rehoboam, consisting of Judah and Benjamin. The king of Judah lived in Jerusalem. And we had the northern kingdom of Israel, under Jereboam, consisting of all the other tribes except Levi. It seems that Levites had no parcel of land so they were pretty much everywhere. As a general rule, Judah maintained better decorum and more favor with God than did Israel. Israel disappeared when it was overrun by the Assyrians, never to be a nation again. Judah remained another 100 or so years until it was overrun by Babylon and the people carried off into slavery. Some 70 years later, they returned to Jerusalem and rebuilt the city and the temple.
If you’re reading Isaiah, keep in mind that he was a prophet in the Southern Kingdom, i.e., Judah.