In all criminal prosecutions, the accused shall enjoy the right to a speedy and public trial, by an impartial jury of the state and district wherein the crime shall have been committed, which district shall have been previously ascertained by law, and to be informed of the nature and cause of the accusation; to be confronted with the witnesses against him; to have compulsory process for obtaining witnesses in his favor, and to have the assistance of counsel for his defense.

United States Supreme Court Case Law

The BJA supported work of the Sixth Amendment Center explores the history of the United States Supreme Court cases behind the right to counsel to understand how the Sixth Amendment developed in the American justice system.

http://sixthamendment.org/the-right-to-counsel/history-of-the-right-to-counsel/