The Washington and Lee University Library is a selective Depository for U.S. Federal Government Publications, as is the W&L Law Library. Thus, tens of thousands of U.S. Government publications can be located via Annie, the W&L library catalog, such as this example.
Here are some additional tools you can use to identify and use U.S. Government information:
Basic finding tool for publications from a wide range of agencies.
Developing (2010- ) gateway to official U.S. Federal Government publications.
Internet search engines limited to government Web pages. (Keep in mind the impermanance of Web information. For example, what about presidential documents?)
Congressional Research Service, Congressional Budget Office, etc.