I'm looking to determine the congressional district based on an address my user is providing. This will avoid having the user to look it up themselves.

Does an API of this sort exist?

Note

Through my attempts to find one, I've only come across these:

• http://www.govtrack.us/developers/api
  (not sure how to submit an an address or zip code however)

  The following resources are available in the API

  ...Bills and resolutions in the U.S. Congress since 1973 (the 93rd Congress).

  ...A (bill, person) pair indicating cosponsorship, with join and withdrawn dates.

  ...Members of Congress and U.S. Presidents since the founding of the nation.

  ...Terms held in office by Members of Congress and U.S. Presidents. Each term corresponds with an election, meaning each term in the House covers two years (one 'Congress'), as President four years, and in the Senate six years (three 'Congresses').

  ...Roll call votes in the U.S. Congress since 1789. How people voted is accessed through the Vote_voter API.

  ...How people voted on roll call votes in the U.S. Congress since 1789. See the Vote API. Filter on the vote field to get the results of a particular vote...

• http://www.opencongress.org/api
  (seems to be a way to find congress information, but not districts)

  This API provides programmers with structured access to all the data on OpenCongress, everything from official bill info to news and blog coverage to user-generated votes on bills and much more...

  This API defaults to returning XML. All queries can also return JSON...

• https://groups.google.com/forum/?fromgroups=#!topic/opendems-discuss/CeKyi_aANaE
  (similar question, no resolution)

  I've been looking over Open Dems, and seeing what's exposed at this point and what isn't. I work with Democrats Abroad, and am interested in using stuff from the lab for their sites.

  I quickly looked over the Precinct API, which does both more and less than what I'd need. An ideal resource would be any way of translating addresses into CD at the very least (getting state district data would be good as well), since that would make it easier for DA's membership to make a difference in races like last month's NY26 race...

Update

I'm looking at the source for the govtrack.us website and the 'doGeoCode' function may be useful.

view-source:http://www.govtrack.us/congress/members

If no one has any suggestions, I will try to go off of what they are doing.