BTMM58A@prodigy.com (MR CRAIG L DUNN) says:
In my book, Iron Men: Iron Will, The Nineteenth Indiana Regiment of the Iron Brigade, I address the subject of the christening of the Iron Brigade in Chapter Five. My source for this is the book, Indiana At Antietam, published in 1911, by the Indiana Monument Commission. The book relates that during the impasse at Turner's Gap, McClellan came riding down the National Turnpike to a point where he met General Hooker. McClellan was greeted by a wildly cheering sea of blue clad soldiers. "General Hooker, if I had an iron brigade I could pierce the enemy's center by taking the gorge on the pike!" Hooker replied, "General McClellan, I have that brigade in my command!" With that, Hooker sent orders to Gibbon to advance his brigade.
I don't know if this is the definitive word, but there is no denying that the name stuck with the brigade following Antietam. Considering that the term was not used prior to September 14, 1862 and was used after September 17, 1862, something between those two dates must have transpired to earn the name. Your two options, South Mountain or Antietam. The brigade's fighting at South Mountain occured after dark, thereby limiting the number of witnesses to the event. Probably only a few officers outside of the brigade knew the import of the achievement at Turner's Gap due to the darkness. To single this brigade out for its performance at Antietam would have been unlikely. My vote is obviously for the scenario as mentioned in my book or something closely resembling it.
On this issue of fact versus fiction or history versus revisionism, I like to think back to Sir Winston Churchill's comments in his History of the English Speaking People when he discusses Robin Hood. After examining the issues he leans in support of the Robin Hood story with the comment, "If it isn't history, it should be."
Hope this arrives prior to broadcast of the 2 Jan CWJournal on the Iron Brigade,
Overall, the five regiments of the Iron Brigade were country men, farmers. Just a bit more than half were native-born Americans and there were substantial numbers of Irish, German, and Scandinavians.
The junior member of the unit, the 24 MI, was recruited mainly out of Detroit (Wayne County) with a fair number of men from nearby Washtenaw & Monroe Counties [Ann Arbor / Ypsilanti and Monroe (Custer Country), respectively] and a scattering from Oakland [just north of Detroit]. There were actually a few from Clinton County [north of Lansing] which at that time was at the edge of next to nowhere. The Detroit men were largely tradesmen -- everything from printers to lawyers; the rest were generally farmers.
The 19 IN was recruited mainly from central Indiana -- Indianapolis, Muncie, Winchester, Franklin, Spencer -- with a company from Elkhart, near South Bend. There were substantial German & Irish contingents, and a fair number of southern-born men.
The three Wisconsin units were from all over the state, and Rock County [Beloit / Janesville (farm country on the Illinois line)] put companies in all three WI units. Of these three regiments, about half were native-born; Irish and Norwegians accounted for about 45%, the remainder largely German with a few English, Welsh & Canadian. The 02 WI was really a hodge-podge of (mostly) city men -- Milwaukee, Madison, Racine, Oshkosh, La Crosse ("God's Country").
The 06 WI had two companies from Milwaukee (one Irish, the other German), but most were recruited from central & western counties. (Lysander Cutler, btw, was a Milwaukee businessman who held office as the city "Fish Inspector").
The 07 WI was also mainly central WI men, but there was also a unit from Chippewa County in the far northwest -- you can bet these guys could use a musket.
Hardly natural born killers (I expect most of the 24 MI men had to be taught to shoot), but life in the old Northwest could be cold, hard & brutal. There were also experienced military men involved with the units from the start (esp. the Wisconsin units, which culled unfit officers before leaving the state), their equipment was good, and their performance in the field reflects the national resolve which motivated these men -- they were both Republicans and Democrats, but there is little evidence of abolitionist motivation left by them.