All Civil War regiments had 1,000 men at full strength. There were ten companies in a regiment, each with one hundred men. Most had this many when they started out, but rarely had anything like this...
The meaning of the number has no particular significance. Permission to form a militia regiment was granted by the US War Department to the Governor of a state. I suppose the "54" was the next...
On the Union Army was the 54th Massachusetts Volunteer Infantry Regiment, the first official black unit that was commanded by white officers. This Infantry Regiment led by Colonel Robert Gould Shaw...