All most nothing is considered public domain in the US. Each country has specific laws though. In the US Copyright is for the life of the author + 70 years. Now there are exceptions to content created before 1978 when the Copyright Act was last revised but to be on the safe side assume that it is protected. And the Berne Convention also makes exceptions for works created between 1978-1988 but these are tricky.

If you want to use something under the Fair Use Doctrine I would strongly suggest getting a legal opinion first or at least doing the necessary research as to the author.

Michael