John A. Buchanan was born on October 7, 1843 near Groseclose in Smyth County. He attended the "old field" school, and local academies at Chatham Hill and Marion. During the Civil War, he served as a Private in Company D, Virginia Infantry, Stonewall Brigade of the Confederate Army. He was captured at the Battle of Gettysburg and remained a prisoner until February of 1865. Adter the war, he attended Emory and Henry College, graduating in 1870. He then studied law at the University of Virginia and was admitted to the bar in 1872. He began his law practice in Abington.

From 1885-1887, he was a member of the State House of Delegates. He was elected as a Democrat to both the 51st and 52nd Congress from 1889-1893. He declined to be a candidate for election to the 53rd Congress. He returned to his law practice and was elected Associate Judge of the Court of Appeals of Virginia in 1895. Judge Buchanan served in this position until 1915.