Buchanan was born to Patrick C. and Margaret Graham Buchanan in Rich Valley, Smyth County, Virginia. He received an A.B. in 1856 and an M.A.
In 1879 he became the Latin chair at Vanderbilt University and later served as president of Emory and Henry College before being appointed VAMC president in 1880. The state legislature replaced the Board of Visitors, who in turn removed all university officials and faculty in June 1880. Buchanan re-assumed the presidency of VAMC in August 1881, but was removed for the second and final time in January 1882.