The standard U.S. Army uniform at the outbreak of the war had acquired its definitive form in the 1858 regulations. It consisted of a Campaign Uniform, a Parade (Dress) Uniform, and a Fatigue Uniform.
During the war, enforcement of uniform regulations was imperfect. Uniforms were adapted to local conditions, the commander's preference, and what was available. For example, shoulder straps began replacing epaulets in dress occasions. As a result, almost any variation of the official uniform could be found as officers and men abandoned some items, adopted others and modified still others.
Described in general terms this uniform consisted of:
Service and campaign
The Service and Campaign Uniform consisted of the following:
A) Headgear: A black felt Hardee hat, the Model 1858 Dress Hat, with one brim being secured by means of a metallic eagle after the U.S. coat of arms of the day. Forage caps were regulation for service and non-dress occasions, while the non-regulation kepi was also widely used.
B) Coat: In Prussian blue, tight fitting and almost knee length, trimmed in arm of service piping along the collar edges; and in the French-peak styled cuff trim, for all enlisted ranks. Company officers wore an untrimmed single-breasted coat, with shoulder straps to signify rank and branch of service. Cavalry and mounted artillery used a short jacket, which were more practical for riding. Field and general officers wore a double breasted version, with the option for black velvet collar and cuffs. A sack coat was also issued as a fatigue uniform, being lined for recruits, and unlined for a service uniform. Rank insignia was worn on the coat, the same as the dress Frock.
C) Greatcoat: In sky blue, with standing collar and French cuffs and a fixed short cape. Officers could wear this or a dark blue variant.
D) Trousers for all enlisted men and company grade officers were sky blue. NCOs had a vertical stripe in arm of service colors. General officers, field officers, and officers on higher staffs wore trousers of the same shade of blue as the coat. General officers had their trousers trimmed with double striping in gold, with all other officer grades wearing piping with their respective branch of service.
The Parade Uniform consisted of the following:
A) Headgear: The hat described with trimmings in the arm of service colors. Some units such as marines and mounted artillery retained shakos for ceremonial purposes.
B) Coat: The same described (frock or short shell-jacket) with metallic epaulets resembling scales. Officers wore French-type epaulets and a sash.
C) Greatcoat: As described.
D) Trousers: As described.
The Fatigue Uniform consisted of the following:
A) Headgear: A forage cap with a floppy crown. Officers tended to privately purchase more elaborate versions after the French Army model subsequently known as chasseur caps. Generals wore a variant having a black velvet band. Insignia was pinned on top of the crown or -in officers- in front of the cap.
B) Coat: A cheaply made dark blue sack-coat of a simple and unsophisticated design, having a loose cut, fall collar, and no pockets.
C) Greatcoat: a large sky blue overcoat double-breasted for cavalry, single-breasted for infantry. Both had capes
D) Trousers: sky blue baggy wool trousers cut with pockets. Officers had dark blue or uniforms tailored to suit individual needs.
In general terms, as the war went on, the service uniform tended to be replaced by the cheaper and more practical fatigue uniform.
A rifle green coat was issued to Berdan's Sharpshooters, 1st and 2nd Sharpshooter Regiment as an early form of camouflage. These had black rubber Goodyear buttons that would not reflect the light and give away the sniper's position.
Marine bandsmen wore red. Infantry musicians had braid on the front of their uniforms, known as a birdcage, in the same color as the facings.
Troops from Ohio or New York were equipped with dark blue shell jackets with shoulder straps and 9 brass buttons down the front and colored tape around edges denoting their branch of service. Depending on the unit, there are variations of this pattern jacket. The Veteran Reserve Corps were issued a similar pattern but in sky blue with navy blue tape. The number of buttons on these jackets varied between 12 and 8. Some had shoulder straps, belt loops and piping while others did not.
One of the more unusual shell jackets was worn by the 79th New York. It resembled the doublet worn by the 79th Highlanders in the British Army and was worn with a Glengarry cap, sporran and kilt for full dress or tartan trews and a kepi when on campaign.
Buttons featured the US eagle which originally showed on the eagles' shields, letters denoting the soldier's branch of service: I for Infantry, C or D for Cavalry (then known as Dragoons), A for Artillery (and on some earlier uniforms then still in use: R for Rifleman, V for Voltigeur). This was done away with early in the war to cut costs; although officers continued to use such buttons well after the Spanish–American War.
Later in the war soldiers of all branches were issued loose-fitting blue sack coats with 4 brass buttons, based on the civilian work jacket, which remained in service during the Indian Wars. However, most of the artillery and cavalry preferred to wear the color-trimmed shell jackets because of their appearance and comfort. By mid-war volunteers were issued a lined version of the sack-coat.
Officers had to purchase their own equipment, and thus tended to wear tailor-made uniforms. The frock coat had epaulettes, (for dress occasions), and shoulder straps, (nicknamed sardine boxes by the men), and was first issued during the Mexican War. These coats were single-breasted for lieutenants and captains and had between seven and nine buttons. It was double-breasted for senior officers and generals with black velvet facings and buttons placed in orders of twos and threes according to rank.
On campaign many officers, including Ulysses S Grant wore sack coats, either private purchase or of the type issued to enlisted men with shoulder boards from the frock coat added to show rank.
High-ranking mounted officers would sometimes wear double-breasted shell jackets in dark blue. These had the same domed buttons and velvet collar and cuffs as the frock coat.
Shirt - The most common color for the army-issue shirt was gray, followed by navy blue or white. The shirt was made of coarse wool and was a pullover style with 3 buttons. It was often replaced with civilian clothing such as a white linen or plaid flannel shirt sewn by the soldier's family.
Bright red overshirts were often worn as uniforms by volunteer regiments early in the war, modeled on the shield-front shirt worn by Victorian firefighters.
Overcoat - Single-breasted for infantry, double-breasted for cavalry with a rain cape. On campaign this was sometimes replaced with a rubber poncho that doubled as a groundsheet. Officers' greatcoats were made of dark blue wool and had black braid on front and on the cuffs.
Depending on region, unit officers' preferences, and other variables; Cadets and the state militas occasionally wore gray.
The 7th New York National Guard Regiment, (among others), wore cadet gray tail-coats with matching trousers and dark blue epaulettes with white fringe, and 1830s style shakos, as late as 1861. The fatigue and service uniform of the 7th New York was a single-breasted shell jacket, with a 9-button front, and black cuff flashing and shoulder straps, with piped collar trim; and a cadet gray kepi, with a piped crown and dark blue band. This appearance, with their white dress gloves, gave them the nickname of "Kid Glove", when the 7th New York arrived in Washington City, in 1861.
Hardee hat - Aka "Jeff Davis Hat". Black with eagle badge keeping the left side of the brim pinned up. For parades an eagle feather was added, with brass designating the soldier's regiment, company and branch of service (bugle for infantry, cannons for artillery or sabres for cavalry). Western units like the Iron Brigade preferred the Hardee hat as its wide brim provided protection from the sun and rain. These hats were personalised by the men, usually shaped into civilian styles like the centercrease, which was the precursor of the cowboy hat.
Kepis were worn on campaign and for fatigue duty. The design varied from a tight-fitting cap resembling the one adopted by the French in the 1840s to a tall floppy "bummer's cap" described by the troops as resembling a feedbag. The leather peak could be stiff and rectangular or crescent shaped (known as the McDowell pattern). The hat band was sometimes a contrasting color to the normal blue: yellow for cavalry, red for artillery, or green for medics and soldiers belonging to the Irish Brigade. Officers' kepis might have black or gold braid to display their rank. Early in the war kepis were supplied with a waterproof cover. Other troops purchased a "havelock" which, like the contemporary Foreign Legion cap had a neck flap to protect the wearer from the sun. The havelock was made of a grayish-blue cotton mesh and was not liked by the troops, who usually used them to filter tea or coffee. So their issue was discontinued in the later years.
Many troops would replace their regulation kepis with civilian hats (normally in black). Popular styles included the slouch hat with either a flat or round top (the latter was issued to the Garibaldi Guard with black feathers added to resemble the Italian bersaglieri hat), pork pie hat, telescope crown hat, flat cap, bowler hat or smoking cap (worn in camp when off-duty)
Marines were issued tall leather shakos before the war but in the field these were replaced with kepis (often with the red enamelled brass M badge from the shako added)
Early in the war the Mexican War era M1839 forage cap was still in use among some regular soldiers. This peaked cap with a neck flap had officially been replaced by the kepi in 1858, but continued to be issued by quartermasters eager to use up old stock.
General officers could also wear for undress order a cocked hat with black ostrich plumes and a black rossette surmounted with the U.S. eagle either metallic or embroidered.
These were sky blue with tin buttons. NCOs had a dark blue (infantry), red (artillery) or yellow (cavalry) stripe down the leg. However, junior NCOs which included corporals, wore a French blue stripe down the seam of the trousers.
Officers wore navy blue trousers with a black or gold stripe.
Jefferson Davis Boots – Black, rough side out with hobnails and heel irons resembling modern-day dress boots. Recent research suggests smooth side out boots were equally common for volunteer regiments.
Cavalry and artillery were issued calf-high riding boots, originally designed for the drivers of artillery limbers. Some also wore thigh-high trooper boots as protection from the elements and in imitation of European cavalry.
Gaiters were issued to regular troops, sharpshooters, zouaves and the Iron Brigade but were quickly discarded as impractical.
The enlisted infantry uniform was completed with a black leather belt and oval buckle with the letters US. Officers, NCOs and cavalry troopers were equipped with a sword belt with a rectangular buckle with eagle motif.
Rank was displayed on epaulettes (dress occasions) or shoulder straps(field duties): no insignia for a second lieutenant, one gold bar for a first lieutenant, two gold bars for a captain, a gold oak leaf for a major, a silver oak leaf for a lieutenant colonel, a silver eagle for a colonel and one, two or three silver stars for a general, depending on his seniority.
The color of the shoulder strap fields - with trims in gold braid - were as follows:
