Infantry and ArtilleryCorps - contained 3 divisions and an artillery reserve battalion, commanded by a Lieutenant General.
Division - 12,000 men, 3 infantry brigades (typical), 1 artillery battalion, commanded by a Major General.
InfantryInfantry Brigade - named for a famous or current commander, 4,000 men, 4 regiments (typical), artillery battery, commanded by a Brigadier General, staff normally included an aide, quartermaster officer, commissary officer, ordinance officer, inspector, and clerks.
Infantry Regiment - named by a number and state, 1,000 men, 10 companies, commanded by a Colonel, staff included a Lt Colonel, a Major, Adjutant, Quartermaster, Surgeon (Major), 2 Asst Surgeons, Chaplain, Sergeant Major, Quartermaster Sergeant, Commissary Sergeant, Hospital Steward, 2 principal musicians.
Infantry Company - 100 men formed into 2 platoons, commanded by a Captain, included a 1st Lieutenant, a 2nd Lieutenant, a 1st Sergeant, 4 additional Sergeant's, 8 Corporals, approximately 80 privates, 2 musicians, and a wagonneer.
Infantry Platoon - 50 men formed into 5 squads, commanded by a Lieutenant.
Infantry Squad - 10 men, commanded by a Sergeant or Corporal.
Artillery Regiment - 3 battalions, Artillery regiments virtually never fought as a regiment, rather the battalions were distributed to Corps and Divisions.
Artillery Battalion - 3-5 batteries, commanded by a Lt Colonel or Major, early in the war the battalion was usually split into batteries that were typically assigned to support a brigade. Later in the war, the batteries often were massed and the battalion fought as a unit.
Artillery Battery - 4-6 guns, 100 men, commanded by a Captain, staff included a 1st Sergeant, quartermaster sergeant, privates (teamsters, artificer, blacksmith, farrier, bugler, guidon) an artillery battery typically would have 6 caisson and limbers in reserve and a field forge.
Artillery Section - 2 guns, commanded by a Lieutenant.
Piece - 1 gun and 1 limber wagon, 8 (minimum) men, 12 horses, commanded by a sergeant, 2 corporals (gunner & chief of caisson), privates (cannoneers, drivers, extra men).
Cavalry Corps - 3 divisions commanded by Lieutenant General.
Cavalry Division - 2-5 brigades, commanded by Major General.
Cavalry Brigade - 2-5 regiments, commanded by Brigadier General.
Cavalry Regiment - 3 battalions, Commanded by a Colonel, staff includes a Lt Colonel, Major, Adjutant, Quartermaster, Commissary, Surgeon, Asst Surgeon, Sgt Major, Quartermaster Sergeant, Commissary Sergeant, Saddler Sergeant, farrier, and 2 hospital stewards.
Cavalry Battalions - 4 companies or troops.
Cavalry Squadron - 2 companies or troops
Cavalry Company (troop) - 40-100 men, Commanded by a Captain, includes 2 Lieutenants, a 1st Sergeant, Quartermaster Sergeant, Commissary Sergeant, 2 additional Sergeants, 4 Corporals, 1 Farrier, 1 Blacksmith, and 1 Musicians (bugler)