There are many strategies for finding relevant US government resources. As stated above, a great starting point is the UCSD US Government Information Research Guide. The databases, websites, and print guides/indexes listed below are also excellent. Several of these resources will help you identify specific publications (with call numbers that you can browse around to find more) that will have information on your topic. Finally, you can simply go to the shelves with print documents (Geisel 2W) and browse by call number. In order to find out which call number to browse in, you need to understand that US government documents and publications are organized by the Superintendent of Documents (SuDocs) Classification Scheme, which is based on US government agencies. In order to find out what letters (stems of classification numbers) have been assigned to different agencies, you can use the list (scroll down to the bottom of the page) provided by the US Federal Depository Library Program.
The UCSD (US) Census Research Guide has many more search suggestions than are listed here, but here are a few useful sites and databases to know about: