The University of Montana Mansfield Library is one of many across the country, meaning that UM students and members of the general public have in-library access to both new and historical government publications. Some, but not all, government publications are available online, so people who need access may need to visit the library themselves.
As a Federal Depository Library, Mansfield Library is dedicated to providing free and open public access to government documents and publications. Many of these are available online and can be accessed through Mansfield Library's public internet terminals. Some are only available in hard-copy, however, whether as a book, pamphlet, or microfilm/microfiche. The library is currently working on entering back issues into the library catalog, but that project is not yet complete. The collection from 1976-present is up to date, but materials from earlier than that may be difficult to find.
The U.S. Government is a complex body of departments, agencies, organizations, and committees, and tracing the specific information you need can appear to be a huge task. Seeking information is really a matter of starting broadly, then narrowing down your search. This guide is designed to explain the broad structures of U.S. Government and give you the tools to start aiming your search in the right direction.
This chart from the U.S. Government Printing Office maps out the major divisions of the government.
If you are not quite sure where to begin your search and asking a search engine gives you too many hits to find anything useful, try identifying which department or agency within the government may offer information on your topic. From there, you can search individual sites.