Who is Clarence Earl Gideon from Gideon's Trumpet and what is their importance?

Gideon is a fifty-one-year-old white man imprisoned in Florida who makes an appeal with the United States Supreme Court. Gideon's claim is simple. He believes that the U.S. Constitution assures him of the right to an attorney at his trial, even though he's not able to afford one on his own. Gideon makes the appeal for himself, having fallen into that category of prisoners who wants to appeal but has no access to an attorney to write on his behalf. Gideon's appeal is first rejected because it didn't include the appropriate documentation but he makes the necessary changes and resubmits, putting it in line for consideration by the Supreme Court.