Does anyone have the slightest idea as to the time frame and location of all the districts and the capitol city?

I'm thinking it has to be a long time after the fall of the United States and Canada. I think this because of Coin bringing up a Republic, which she said happened a long time ago. I would like to say District 12 is around the Michigan area because of the trees and the type of weather they recieve, but I'm not for sure. I'd also like to think the Capitol City is somewhere that is rather important to us today. So maybe New York or California? I'm only guessing. Thoughts?