Author Jesse J. Holland, speaking on PBS's News Hour stated: "The Statue of Freedom was created by an American art student named Thomas Crawford. He actually won the competition to decide which statue would crown the Capitol. He put together a statue of a woman. And, on top of the statue, he put a liberty cap, which is a small hat."
"The person in charge of the Capitol construction vetoed the whole project. The person in charge was Jefferson Davis. And, when he saw the picture of the Statue of Freedom, he noticed the cap that was on top of the statue. And, being a student of Roman history, Jefferson Davis knew that the only people in Roman history who wore liberty caps were freed slaves."
"Well, Jefferson Davis, who goes on to be the president of the Confederacy, says, there's no way he's going to allow them to put a statue of a freed slave on top of the Capitol. So, he tells Thomas Crawford that, you either change the statue, or we're going the commission to someone else."
"Now, like I said, Crawford was an art student. Art students always need money. So, instead of changing the statue, what Thomas Crawford did was, he took the liberty cap off, and he put an American eagle helmet on. So, most people look at the Statue of Freedom now and they think, this is the statue of an American Indian on top of the Capitol. No, it's not. It's actually a statue of a freed slave with an American eagle helmet on top." -- Jesse J. Holland
source: Transcript PBS News Hour, "Author, Jesse J. Holland, Offers Insights on Slavery, the Capitol, and Obama's Inauguration" 16 Jan. 2009