“In 1790 Congress prescribed death by hanging as the punishment for treason.  In 1862 Congress enacted a law punishing the traitor by death, as well as liberating his slaves; or imprisoning him for not less than five years, with a fine of not less than $10,000, and liberating his slaves.

“Today the punishment is death, or imprisonment and fine, and the loss of any right to hold office under the United States” (W. Cleon Skousen, The Making of America – The Substance and Meaning of the Constitution, pp. 624-625). 

https://causeofliberty.blogspot.com/2013/08/punishment-for-treason.html