Brigadier General Union Army.......GE where do you come up with these photos
Edit - He was a brigadier general in the Union Army, but we needed the name.
Some players seem to be much better at identifying photographs than I am, but I know there is a Wikipedia article with a list of Civil War generals (Union) that lists all the generals with photographs of the vast majority of them. I usually use that website when a question asks for the identification of a Union general, though it's tedious.
I am not aware of such a website featuring pictures of more than a select number of Confederate generals.
John Gross Barnard.
"With the outbreak of the Civil War, General Barnard served as Chief Engineer to General McDowell in the First Bull Run Campaign. Next, with the rank of Brigadier-General, he acted as the Chief Engineer to the Army of the Potomac in the Virginia peninsular, serving Major General George B. McClellan. When the confederate army advanced into Virginia, he was appointed Chief Engineer of the defenses of Washington, and was promoted to Lieutenant-Colonel of Engineers in March 1863."
"In 1864, he was appointed Chief Engineer, and was on the staff of General Grant in the Richmond campaign. He was made Major General at the end of the Civil War for "gallant and meritorious services in the field," and was promoted to Chief Engineer of the Corps of Engineers December 28, 1865. Although he was promoted to full rank Colonel of Engineers, upon General Totten's death, he asked that the nomination be withdrawn. He served out his career as Chief Regular Army Engineer until his retirement in 1881." Source- National Park Service