$100 bills are the largest denomination still in print. The $500, $1,000, $5,000, and $10,000 bills were discontinued in 1969 because they were rarely used. Those which remain in circulation are still legal tender, but may be worth a bit more than face value to collectors.
The largest note ever printed is the $100,000 gold certificate, issued only to the Federal Reserve Bank by the Treasurer of the United States. These were printed by the BEP from Dec. 18, 1934 through Jan. 9, 1935. None of these notes, which featured Woodrow Wilson on the front, were circulated among the public.