User blog comment:Robert.j.watkins/Where is Starling City?/@comment-6005209-20141002181827

An interesting question. I don't think this is ever specified on the TV show of course. In the comics Star City is usually on the West Coast - as is Coast City.

In one of the first season episodes, Tommy's car has a license plate that is not from any specific state but does have the motto - "Land of Mist"

Also keep an eye out for the maps in the show, they seem to be based on Seattle. And they look like west coast with a large area of water to the left.