All copyrighted work published after 1978 is 70 plus the life of the author. That means that the copyright is good until the author dies, and then there is an additional 70 years. For works created prior to 1978, the rules get VERY complicated. This includes what year the work was created, what year it was filed with the copyright office, whether or not the author ever published the work, if they renewed their copyright, if they ever assigned the copyright to someone else, if the other person renewed them, if they died, if their heirs renewed the copyright, etc.
Just a small note, part of the reason why the timing is so complicated is 2 fold. First, the constitution uses the language of "limited time" -- which means that copyrights cannot be infinite (or perpetual). Thus congress MUST pass legislation detailing when the copyrights end. Additionally, people have dubbed these copyright extension laws "Mickey Mouse" laws because much of the force that went into their creation (the main lobby) was Disney, working to extend their copyright on Mickey Mouse (created in 1928). Each time mickey mouse was due to expire, the lobby went into full blast and congress passed an extension to the copyright, that would cover disney's property. This is part of the reason why they are so complicated and so frequently amended. (It used to be 20 years, with 20 years if you renewed... and other complicated schemes).