I recommend you begin your search for government information in the Catalog of U.S. Government Publications, or CGP, which is the central database for publications from across all areas of the federal government. Much of what you find here will be available in full-text online; to access the full-text, click the link in the right-hand column labeled "Internet Access."
Here is a selection of U.S. government departments and websites that could be relevant to your research: