Complications of the U.S. Public Domain
Here is a useful and informative article about copyright by Peter Hirtle, Senior Policy Advisor at Cornell University Library. It includes a section on "The confusing case of government works."
- When Is 1923 Going to Arrive and Other Complications of the U.S. Public Domain by Peter B. Hirtle,Searcher 20.6 (2012): Searcher 20.6 (2012).
Think 1923 is the magic year? Think again! "Probably the oldest work still protected by copyright in the U.S. is a letter from John Adams to Nathan Webb written on Sept. 1, 1755."