From William Ely's The Big Sandy Valley:

"A son-in-law of Judge Wm. Weddington, and brother-in-law of R. M. Weddington, is one of the prominent physicians in the Sandy Valley. He is a man of wealth, and great energy. He was lieutenant-colonel in the 39th Kentucky Infantry, United States army. He came from Virginia to Sandy in about 1843. He is a strong Republican in politics" (154).

From "Pioneer Valley Industrialist Was Physician, Union Leader", in the Floyd County Times, Jan. 18, 1962, by Henry P. Scalf:

At the beginning of the war, the Confederates came for him at his home in Industry (modern-day Boldman, Pike County, KY), but from his bed he convinced them that he was too ill to travel. They left him and he decided to be gone if they should return. Ferguson and Washington "Wash" Stratton both hid from May's soldiers in a rock shelter. When "Bull" Nelson's Federals drove May's men from the area, Ferguson and Stratton came out of hiding.

John Dils and Lindsey Layne convinced Ferguson to join the 39th, and he accepted a position as surgeon while his friend David Mims accepted appointment as lieutenant-colonel. He was first assigned to Company K. Ferguson claimed after the war that he was on the scout that discovered Marshall's position for Garfield at the Battle of Middle Creek. He may have been on hand to treat the wounded. Ferguson was at the Battle of Bull Mountain, but his participation was brief. He was unseated by a skittish horse and his leg was trampled. He was able to remount, but his ankle was broken and caused him problems for a while.

Ferguson took command of the 39th on Jan. 14, 1864. He was the second of the regiment's commanding officers; his friend David Mims of Pike, then Boyd, County was the last commanding officer. Upon the regiment's mustering-out, the men of Company K presented him with an engraved sword and a fine watch.

After the war, Ferguson continued as a physician and was instrumental in trying to get a railroad into the region to develop the coal resources.