Yes, they are still legal tender and recognized by the U.S. Gov. If you were to bring them to a bank, they would give you face value. However, if you were to bring one into a store, i doubt the clerk would accept it because they probably have never seen or heard of anything over a $100 dollar bill. By the way, those bills, depending on condition, are possibly worth double their face value. You should check with a reputable collector.
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They are legal tender, but you probably would not be able to use them at most places.
As the other attorney said, they are far more valuable as collectibles then they would be as money.
Don't cash them in. Instead, take them to someone who deals in coins and such. They can find you a buyer.