Joseph Holt was a prominent figure in American history, known for his role as a lawyer and politician during the 19th century. He served as the United States Postmaster General under President James Buchanan from 1859 to 1861. Holt was also a strong advocate for the Union during the American Civil War, which began shortly after he left office. In addition to his political career, Holt was a key figure in the legal proceedings against the conspirators of Abraham Lincoln's assassination. He served as the judge advocate general of the U.S. Army, overseeing military trials and ensuring justice was served during a tumultuous time in American history.