The Catalog of Government Publications is run by the Government Publishing Office. The catalog will work, but it will not be updated after the shutdown begins. Also, some of the PURL links in the catalog (purl.gpo.gov) may not work during the shutdown.
CLIO, Columbia's public catalog, is very helpful in finding United States government information at Columbia. The best search strategy is to use CLIO's Advanced Search option. Once at the Advanced Search screen, change the first drop-down to Author and enter United States in the box next to it:
Leave the remaining drop-downs as Any Field and enter your search terms in those boxes (think of broad search terms for this step). You may also change the second drop-down to Author and add the name of a particular agency or department to find publications from that agency. You also have the option to limit by date, format, or Columbia library location if needed.
Many, but not all, of the online government titles in CLIO can be accessed by anyone. If you need a tangible title, note its physical location, call number, and status--CLIO can also text you this information.