Terry, the only Captain Buchanan from that area that I know of is Capt. Pleasant Wilson Buchanan. He was a professor of mathematics at Cane Hill College before the war. When the war started he raised a volunteer company, the Cane Hill Rifles, which became Co. D of Gratiot's regiment of Arkansas State Troops. When the State Troops disbanded after the battle of Wilson's Creek, Captain Buchanan raised another company, which became Co. H, 15th Northwest Arkansas infantry. He was captured at Pea Ridge and held as a prisoner of war for several months. Another captain was elected in his place during his absence. His record is very murky after that. He was forwarded from Johnson's Island, Ohio, to Vicksburg, Mississippi, for exchange on September 1, 1862. The last record states that he drew pay and clothing from the quartermaster at Little ROck on February 21, 1863. He signed the receipt as "captain, Co. B, Brooks' regiment." This is presumably the 34th Arkansas Infantry. Although there are several Buchanan's in Co. B, there is no record of Captain Buchanan.

I ran across a couple of brief biographical sketches several years ago, both published by the Washington County Historical Society. One sketch states that Captain Buchanan was captured and hung by the Federals at Cane Hill on February 21, 1864, while on recruiting service. The other states he was killed by Pin Indians on February 25, 1864. His gravesite at Cane Hill Cemetery says that he died on February 21, 1864.

That's all I know about this officer. I hope this helps a little.