James Henry Porterfield is my husband's GGG Uncle and his namesake. My Jim's Dad left us a transcribed copy of James Henry's Civil war diary. He was 1 of 6 brothers who fought for the Union. His Dad was John Duff Porterfield CSA from Holly Springs, MS now a suburb (practically) of Memphis. James Henry was 24 when he joined the union at a muster in Pine Bluff, ar. He spent almost his entire career in his home area fighting at Shiloh, Vicksburg and sneaking off eating dinner with friends, family and enjoying an occasional "romantic" trist. He watched a brother (Theopholis Porterfield) die at a Memphis hospital while they were both in one brother against brother and spent time in prisoner Camps at Cahawba, AL and was still in Andersonville as the war came to the end. Porterfield is not a common name so is he mentioned in any of the info you have on the 18th. He started in de Golyer's battery and switched many times as he grew up in the area of Grants interest in taking down Vicksburg.