In a previous post, we discussed the history of Milwaukee's flag from 1897 to today, including one small detail on the current flag, introduced in 1954:
In the lower-left quadrant of the gear is a small flag, usually identified as a "Civil War Banner" or "Civil War-Era".
It has also been suggested that this isn't from the Civil War at all, but is instead a service flag.
These flags became widespread during World War II, and quickly became iconic. The blue star was a symbol of hope, the gold sacrifice. This is clear in the propaganda posters of the time:
You can see a service flag in this cartoon by Milwaukee Sentinel artist Lou Grant. On the back wall of our fictional Brewers tavern, a service flag remembering Brewer owner-turned-Private First Class Bill Veeck.
So, could this have been a service flag? It certainly seems possible, but I'm leaning against it. The war was still fresh in the public's mind in 1954, and adding one to Milwaukee's Frankenflag would have been an excellent way to recognize the city's war contributions. On the other hand, the design isn't quite right. Service flags were white with red border all around, whereas this is clearly a red/white/red horizontal tricolor. Seems unlikely to get the design wrong specifically because the war was so relatively recent.
I'm not ruling out the possibility, though. More research is needed on this particular chapter in the city's history.