Camp Randall Quartermaster
Original Civil War Uniforms

CIVIL WAR TROUSERS
Note, how baggy and long the trousers are on this soldier. (As soon as he left the studio, he probably rolled up the trousers to for a "better"fit ).

Sckuylkill Arsenal Infantry Trousers - Smithsonian Institution
Notice the rise in the back of this pair of SA trousers. This is common on All Civil War trousers. The trousers are made of 21 oz wool kersey.
On this pair of trousers, the watch pocket is built as a separate piece, above the waist (Common to SA trousers). The bottom cuff has a facing that is "hand sewn' around the top of it.
Notice that the waist band on original trousers gets smaller as it goes to the back vent opening. Also, notice that the two pieces of the gusset do not match together exactly. (sloppy workmanship)
On this pair of SA trousers, The facing inside the fly opening is made of "cotton drill" material, common to SA. Notice that even though the waist band gets smaller, the inside faccing of it (made of cotton drill, stays the same size. It is hand sewn down at the bottom. There is a wool facing sewn around the vent opening and hand whipped down. On this pair the top part of it is covered by the waist band facing.
William Deering Contract Trousers - The Smithsonian Instatution
Again, notice the "rise" in the back gusset of the trousers. The top of the side seam pockets on Deering trousers, started about 1" below the waist band. The trousers are made from 21 oz. wool kersey.
This pair of Deeing trousers has the watch pocket built into the waist band. This photo also give a good view of the narrowing of the waist band (large in front, but gets smaller as it goes around to the vent split)  Notice the drill reinforcement STILL stays the same size, but stops short of the wool re-enforcement around the vent opening.
An excellent  view of the back gusset on Deering trousers and the narrowing of the waist band.
Another excellent view of the inside of the waist band and rear vent re-enforcement. The inside fly is backed by brown polished cotton.
A very good view of the cuff of the trousers. Notice the bottom facing and how it is hand whipped down  The vent split has a cotton drill re-enforcement above it, hand whipped down
H. F. Harkness Contract Trousers - The Smithsonian Institution
Again, notice the "rise" in the back of the trousers. The trousers are made out of 21 oz kersey wool
On this pair of trousers, the watch pocket is built right into the waist band. Again, the cuff has a separate facing, turned over and hand sewn down.
A good view of the inside of this pair of contract trousers. The facing inside the fly opening is made of brown polished cotton. The facing for the waist band still remains the same size, even though the actual waist band is narrowing as it comes from the front of the fly opening to the vent opening in back. There is a wool facing re-enforcing the back vent. It is hand "whipped down". around the vent opening. On this pair,unlike the SA pair it is on top of the waist band facing.
The yoke on this pair of trousers differs greatly with the cut of the yoke on the SA trousers. Again, notice how it still does not "match up" exactly. Again, you can see the narrowing of the waiste band in the back.
R & W Contract Trousers - The Smithsonian Institution
Again, notice the rise in the back of the trousers. The trousers are made out of 21 oz  wool kersey.
This picture gives a very good view of the cuff vent re-enforcement. This was either made of cotton drill or wool and hand sewn on just above the "split on the cuff. (In the majority of Civil War trousers, the re-enforcement was made of cotton drill ) .Also, notice the wool facing for the vent split This is common to all Civil War trousers.  It is sewn on, turned over and hand sewn down.
The back yoke on this pair of trousers is comletely different in shape than the previously ones. Again, notice how the waist band narrows in the back.
This picture give a great view of the back vent reenforcement On this pair of trousers, the facing again covers the waist band facing.   Again, notice that will the waist band has narrowed. but, the inside facing remaines the same width.  Remember, it is hand whipped down at the bottom.
R & W Mounted Contract Trousers - The National Archives
Mounted trousers were made exactly the same as infantry trousers.   Again, the rise in the back of the trousers.  They are still made from 21 oz wool kersey.
Interesting that this pair of trousers is made by the same contractor as the pair previously, but the watch pocket is put in differently (Just like the SA pair). The cuffs are the same as the infantry trousers, except for two buttons added to each side of the end of the legs.
This photo gives a good look at the extra re-enforcement for mounted trousers. All it is, is extra wool re-enforcing the seat and inside leg areas. It is left plain, NOT turned under and "hand whipped" down. also, on mounted trousers the the rear seam and leg seams are turned outward. That is the ONLY differences between infantry trousers and mounted trousers . For a better view and explanation why, see a detailed view in the image below.,
A good look at the bottom cuff of Civil War trousers. You can see the wool facing and how it is hand "whipped" down. The buttons on the mounted trousers are there so that leather straps can be attached to go under the boots/brogans to keep the trousers from pulling up will riding. Again, the difference between infantry trousers and mounted trousers is the extra re-enforment in the seat, the turning of the rear and interior leg seams outward and the extra buttons at the bottom of the leg
The  facing for the fly is made of cotton drill like the SA pair, not the brown polished cotton, favored by a lot of the contractors.  The back wool facing for the vent opening goes under the waist band facing on this pair of trousers.
Mounted Trousers of William Bettes, 6th Ohio Cavalry  ( Photo by Michael Cunningham)
This image, of the trousers worn by William Bettes, 6th Ohio Cavalry  shows a good view of the insides . Notice that the rear seam and the interior leg seams face out, not in. This makes the seams more comfortable against the legs and seat where they rubbed against the saddle.  The raw edges of the seams are covered by seat and leg reenforcement on the exterior side.