Citing government documents in Chicago style generally depends upon the type of document being cited.  A detailed model of how to appropriately cite government documents was created by Bowdoin College Library.  

The more general example for a government document for the Biblography page would be:

Chicago Citation Format
(Chicago Manual of Style, 15th ed., sections 17.270, 17.295)

Structure:

1. Author’s last name, first name, middle initial (if given).
2. Title of document (subsection is placed in quotes, followed by title in italics).
3. Format (omit if it is a printed page).
4. Publisher city: publishing company, copyright date (include as much information as possible such as page numbers).
5. Source (From Library of Congress in normal font), Collection name (in italics). If no collection name, name of division where item is housed with no punctuation.
6. Medium.
7. URL (use bibliographic record URL or shorter digital id if available at bottom of bibliographic record).
8. Accessed date (in parenthesis).