The Iron Brigade was composed of Midwestern regiments from Michigan, Indiana and Wisconsin and fought in the eastern theater of the war. They had a reputation of being a hard-fighting regiment and would usually be in the very hottest parts of the battlefield. They received the name Iron Brigade for sustaining the highest fatalities at the Battle of South Mountain, leading up to the Battle of Antietam.
Then, the majority of the brigade, 1,153 became casualties at the Battle of Gettysburg, mostly on the first day.
I saw pictures of the BGSs for it (Big Green Sign) and here near us we have the medal-looking one with USV (United States Volunteers) in the middle with spokes radiating out for each of the five regiments in it: 19th Indiana, 24th Michigan, 2nd Wisconsin, 6th Wisconsin and 7th Wisconsin.
A Fitting Memorial to a Hard-Fighting group of Men. --RoadDog