It really depends on who prompted you, because it can only be built after you have all the other buildings before it. If you bought Bumblebee Man, you might get prompted to build the Town Hall long before you’re ready for it – I waited for a long time before he could go there and arrange his divorce.

In normal gameplay, building the Town Hall is a 2-part task and it’s prompted by Lisa. Chief Wiggum first has to collect bribes three times. Be sure to keep Lisa free for the end of the third time, so that she can be the one to prompt the building (outraged at all the corruption).

For a full walkthrough see this very helpful link: