Amazon just announced that their Worker Qualification now supports US State locations. It is currently available through their API and is also available through their Web Interface.
It is great to see that Amazon is adding features to their API; just a few months ago they added the ability to support Qualification Sets so that if workers match even one qualification they are permitted to complete a HIT.
This new US State location Qualification feature is available on TurkPrime, as well. The TurkPrime Web Interface will be significantly easier to use than the Amazon Web interface as it will display states as a separate option from countries and also support selecting multiple states based on geographic region like US Northeast, Southwest and possibly using a GUI map. We expect this feature to be available about June 15.
Users of TurkPrime who launched surveys with custom panels have had access to this feature for months. But it's good to know that this feature will be natively supported by the Amazon MTurk API and will be available to a much broader audience.
One powerful application of US State locations Qualification is running surveys with a state by state representation consistent with the most recent census data. This is a feature that is being developed at TurkPrime and is planned for Sept 1, 2015.