Blessmag,
Agreeing with Johan_Steele and Ole, I will also mention in the 1861 Revised Regulations for the Army of the United States, it describes under "Uniform" the "Fatigue Jacket" and how it was to be worn. It is a durable uniform that can withstand the wear of heavy use and not one of a 'Dress' or 'Formal' uniform. Thus, our present Army uses 'fatigues' in daily duties, specialty fatigues as to wear on a daily basis. Only on formal duties the 'dress' uniform will be worn. In the Civil War, there were only two types of uniform. Not the later Army that had several classes of uniforms.
Respectfully submitted,
M. E. Wolf