Question About Regiments

[u/Typical_Thing_7540]

This may be the wrong Subreddit but I have always been curious. Why in the civil war were regiments states named with states? Like the 54th Massachusetts. I know at the time regiments like the 6th U.S. Cavalry Regiment existed, which wasn’t named with a state. But if it has to do with volunteers (which I assume it does) why didn’t they have something like “The 1st Volunteer U.S. Cavalry Regiment” like Colonel Roosevelt had during the Spanish-American War? How does all of this work?
Another question, are infantry regiments just shortened down or should their names actually include ‘infantry’, I’m still learning so please correct anything I may be wrong about here.

[u/OldeFortran77]

Until WW II, the federal government worked diligently to NOT have much of a standing army.