When the first $100 bill was issued it was actually called a Note. In 1862 the first U.S. $100 note was issued. In 1863 you could purchase $100 gold certificates. In 1869 Abraham Lincoln was represented on the note.
These bills were larger than our current currency. They were approximately 7.4"x3.1"
You can find some good information about the $100 note at The paper money experts and some pictures of the bill.
At Wikipedia you can find nearly the same outline however they have an image of the Lincoln note.
Another source with some great images of the Hundred Dollar bill can be found at Matter of Life