I used The World Book Encyclopedia.  I also found information by using The Rourke Guide to State Symbols: Flag, The Rourke Guide to State Symbols: Bird, The Rourke Guide to State Symbols: Tree, The Rourke Guide to State Symbols: Flower, The Rourke Guide to State Symbols: Facts, The Rourke Guide to State Symbols: Songs, and that's what I used for my web page.