“After that.” Jerusalem had been mostly run by ungodly kings and priests (although not all of them were), and that made life hard on the people. In the Messianic Kingdom, Jesus Christ will be king and reign in righteousness (Isa. 11:3-5), and he will restore godly judges and leaders. Then even the people will call Jerusalem, “City of Righteousness; Faithful Town” (which can also be translated: “City of the Righteous, Community of Faithfulness”). Thus this verse is a testimony to the fact that if a society is going to be godly, the leaders must be godly, and in the Messianic Kingdom of Christ they will be.
“Righteousness.” In this context, “righteousness” is doing what is right to God and others. In the Millennial Kingdom, Jerusalem will be called the “City of Righteousness” (or City of Justice) because people will do what is right to God and each other, and Jesus Christ will reign as king over the earth and the Law will go out from Jerusalem all over the world. [For more on “righteousness” having the meaning of doing what is right, see commentary on Matt. 5:6].