Ever wonder where the out of state people in your city came from originally? Or at least which cell phone area code they are hanging on to?
Spokeo has a neat little tool that will tell you the related states, and top 20 cities for all the mobile numbers that aren't from the same area of residence. (Some areas have enough cities represented that they are shown in the state infographic.) That is to say, in Long Beach NY, if you have an out of state phone number, there's a 25% likelihood you have a Florida are code. My own suburb of Los Angeles falls into that giant "Other" group.
My anecdata regarding vehicle license plates mirrors this a bit, with the highest concentration of out of state license plates being New Jersey, Florida, Connecticut, & Pennsylvania respectively.
I know folks in Los Angeles that cherish their NJ, IL, & OH area codes. I'll be holding on to my (310) for a very, very long time.