All Smiles
Uncommon23.2%ObjectiveOptional
Have at least 1000 citizens and an average happiness rating of 75%.
This is easy and can be achieved pretty quickly; any decent city will do it. Keep an eye on the happy icon toward the right of the icon row at the bottom of the screen and address any issues reported there.
Understandably, citizens like low-ish taxes, parks, good services (medical, police, fire, etc) and having education and jobs. Standard stuff, really.