There are many regional accents in the United States. and from these we can often identify a person's place of origin. (When I first went to college in Indiana, people Immediately knew I was from New...

There are many regional accents in the United States. and from these we can often identify a person's place of origin. (When I first went to college in Indiana, people Immediately knew I was from New York.) Why do you think these accents developed as they did? Where did the distinct sounds come from? Is there anyone "correct" American accent?