The movie is called Chinatown for many reasons. The story leads up to a point where everything sort of resolves and it does it in Chinatown. To my understanding most of the Americans think of Chinatowns across the country as dangerous places. Because it is not to their understanding. And the average American citizen fears the unknown. I'm not entirely sure but the crime rate is probably higher in those areas. I mean i watched a lot of movies that takes place in Chinatowns. So anyway the lovely Jack Nicholson plays a character called Jake Gittes and he's this cool, charismatic and smart ex-cop turned private eye. He's a bit of a cynical asshole. Throughout the movie Jake solves mysteries and
stuff. While all this take place, the audience learns bits and pieces of information about Jake's past. That how he used to be a cop and how he couldn't save this one woman from some criminal in Chinatown. So we learn that the woman dies and Jake transforms into an asshole, and scars him for life etc.
Think about what HAPPENS to the guy mentally after the movie, i mean you lose the girl, you lose half your nose, bad guys walk free bla bla. I'm thinking suicide, I mean the same shit happens again at the end of the movie plus the character was probably in love this time. I mean why meet the gal in Chinatown right? There's tons of other places that you can secretly meet up and flee the country or whatever. Anyway it's a movie so it should be interesting. I'm thinking that's why Polanski changed the ending of the script or the title of the movie can be easily called "Happy Endings" .
So I'm thinking the name Chinatown is some kind of metaphor for Jake's mental downfall. I mean you don't learn from your mistakes and get the girl killed yet again. So the character gets no resolution, no closure whatsoever. He sunks deeper in a way. It's a downer. And there's this dialogue at the end of the movie that defines the movie somewhat. Walsh says to Jake "Forget it, Jake. It's Chinatown.". That's more or less the outline of the movie.