The Hunger Games says that the remains of the U.S. are 12 districts. But where are they placed? What states?
In Catching Fire, a map of Panem is visible during one scene. The official map indicates the general location of District 12 in Panem (which, it should be noted, does not occupy the same size as the modern-day United States, due to apparent flooding).
District 12 is in Eastern United States, most probably Virginia, North Carolina, or South Carolina.
Edit: Given that District 12 is the 'coal district', it's unlikely to be North Carolina as the state has no coal deposits, however Virginia has bituminous and semi-bituminous coal deposits in the Appalchian Mountains.