In the United States, corporations are registered with the state government. The states are responsible for registering corporations and laws governing the registration and operation of corporations. Usually, corporations file with the secretary of state, but this isn''t true for all states.
Each state has their own web page which contains contact information. Some states even allow you to check corporate filings online.
State''s websites are usually www.state.(state''s initials).us
Corporate filings will only verify that they exist.
Its also important to know that two corporations in two different states can have the same name while two corporations in the same state can''t have the same name.

Hope this helps
Jsheridan2

If the company is publically traded, you can also look them up at www.secinfo.com, since public companies have to have a lot of information on file with the SEC.