According to US law, all non-secret documents are required to be deposited with the Government Printing Office (GPO) for dissemination to the public through the Federal Depository Library Program (FDLP). Coates Library joined the FDLP in 1964.
Government documents are arranged by a separate call number system - "Sudocs" (short for Superintendent of Documents) system. Items are arranged by issuing agency rather than by subject. A call number for a government document (or "Sudoc" number) will look something like this:
Thanks to Boston College University Libraries for the example above.
Coates Library collects about 25% of the material produced by the federal government, and also has a collection state documents from Texas agencies as well as local San Antonio government publications.