Due to the historically decentralized nature of the government in the United States, there is no single source for locating government documents, and the organization and accessibility of these documents are idiosyncratic, depending on the level and place of government you are researching (e.g. federal, state, county, township, municipal).
Even within the same level of government, the publication, retention, and organization of documents will vary by branch of government (legislative, judicial, executive), and even within the same branch (e.g. executive) you will find variances between agencies, and between the same agency at different periods of time. Prior to the Presidential Records Act of 1978, all presidential papers were considered the personal property of the president, and presidents took their papers with them when they left office.
This section of the guide primarily covers documents of the United States federal government. As described above, documents of the various states are organized differently, depending on the state. A good place to begin for historical documents of the individual states is:
For county, township, and municipal documents, it's best to contact the clerks' offices of those branches of government directly.
For more help finding government documents, contact the Library's unit of Research and Information Services.
The judicial branch, at all levels of government, is probably the least transparent, and its documents are often the most difficult to access.