An opponent of secession, Butler represented Johnson County at the East Tennessee Convention in 1861, and afterward joined the Union Army.

Butler was censured by the House of Representatives in March 1870 for receiving payment in return for recommending someone for admission to the U.S.

[3] At the age of 21, Butler began reading law with Carter County attorney Carrick W. Nelson.

[4] Described by fellow Unionist Oliver Perry Temple as "unshrinking" and "outspoken,"[5] Butler was arrested by Confederate authorities and charged with treason in 1862, but was acquitted due to lack of witnesses.

That same year, he was elected to the Tennessee Senate, but resigned to accept an appointment by Governor William G. Brownlow as judge of the state's First Judicial Circuit Court.

[6] In 1867, Butler was elected as a Republican to the Fortieth United States Congress, winning over 86% of the vote in a race against Democrat James White.

[7] He was censured by the House of Representatives on March 17, 1870, for accepting payment in return for recommending the appointment of a cadet to West Point (a vote to expel failed).

[7] Though the state legislature gerrymandered his district,[1] he was nevertheless reelected to a fourth term in 1872, winning 56% of the vote in a race against William B. Carter,[7] the leader of the East Tennessee bridge-burning conspiracy.

In a letter to editor William S. Speer, who was compiling information for his book, Sketches of Prominent Tennesseans, Butler stated: If my time were to go over, I would attend to my profession and nothing else; I would never go into politics; there is no money in it, it is a dog's life; the politician is a pack-horse for everybody, has to go everybody's security and neglect one's private affairs.

His private residence in Mountain City, the Butler House, is listed on the National Register of Historic Places.