USA.gov provides listings of federal government phone numbers along with links to government agency and state government listings. State government websites, such as California's ca.gov, provide numbers for state departments and agencies.
To find federal government phone numbers on USA.gov, scroll down the page to the section entitled Government Agencies and Elected Officials. Under Contact Federal Government there are listings by government agency or topic. The agency listings also provide links to agency websites, which often have more specific contact information than what is provided by the USA.gov listing.
The USA.gov website also has listings for state and tribal government websites. From these state government pages there are links with contact information or agency listings. For instance, the California State government webpage, at CA.gov, lists contact information under the Contact Us link at the bottom of the main page. On the New York State government website, at NY.gov, there is no specific contact page. Instead, visitors have to find the agency they are interested in, using the links and the bottom of the NY.gov main page, and then use that agency's contact page.
USA.gov also provides contact information and links for elected officials in the Government Agencies and Elected Officials section. The individual state legislature websites are all organized a little differently. Look for contact links or legislator listings.