Information about private companies is more difficult to acquire. Unlike a publicly traded company, a privately-held company does not have the same filing requirements with the SEC. However, privately-held companies may file some SEC reports (usually S Forms or 10-Q) when required for raising equity.
See also: State-level resources
Companies must file in the state they are registered or incorporated. Visit the state's home page to identify any publicly available filings and the agencies regulating the business registrations. Articles and Press Releases will contain information about private companies. Also consider searching local newspapers near company headquarters.