I'd wouldn't consider you being "from" wherever you're located at that point in life. I think the pivotal years from about 10-18 are where you're from.
Those ARE NOT the pivotal years of most people lives...People go through drastic changes after high school...
Who you are and what you do in your 20's will have a bigger impact on were you end-up in life...
To answer the OP's question,
I would say you are from wherever your accent and sometimes race/ethnicity is from...
For example, if you have a Southern Drawl, you will never be considered a New Yorker by most New Yorkers...
If people, in the city in which you currently reside, have a reason to ask you "you sound/look different, where are you from?" then in my opinion, you can't claim that area...