Accurate undergarments will affect the comfort and fit of the over clothes, as well as help to help distinguish between a costume and reproduction garments.
Men’s drawers for the mid 19th century were made of white cotton; canton flannel and osnaburg are both good choices. Drawers are the first layer worn next to the skin to protect trousers from perspiration, to cut down on laundering of the trousers, as well as to protect the skin from rough fabrics. Drawers button shut at the waist.
Undershirts were worn as a means of keeping the outer shirt clean, and for cooling or insulating the body. Undershirts were stout cotton muslin, canton flannel, wool flannel, or cotton or wool knit. Knit options were very popular and common in the mid 19th century. Undershirts fit closely to the body.
Socks were made of wool or cotton. Some men would wear silk socks for nicer occasions. Socks were either hand or machine knit. Knitting of the mid 19th century was done on smaller needles and finer yarn than most modern knitting. Colors should be black or white, or of a variety of muted dark colors.
A sock pattern from the Sanitary Commission, 1865, can be found Here.
White cotton shirts are a good wardrobe staple for most any mid 19th century impression. Cotton shirting was a popular material, but linen was used earlier in the era, and by certain people. Styles were transforming in the mid-century from square cut, ie, composed of mostly square and rectangle shaped pieces to tailored shirts, known as “French Cut” shirts.. There were many styles between these two variations that show the progression of the fashion development. Most would have long sleeves and a button-front placket and the back and top of the shoulders of men’s shirts were lined to prevent early wear through. Collars and other details, including decorative pleated shirt fronts of different materials, varied. Depending on what years you are portraying as well as your socio-economic class, your style of shirt could vary.
By the mid-19th century there was a fairly large ready-made industry for shirts, thus making white shirts affordable to most classes of people.
Similar style shirt would sometimes be made of wool or cotton of drabber colors or woven checks, prints, stripes and plaids. These were not as prevalent as the standard white shirt
Overshirts were commonly made of wool,including wool flannel, natural linen or other stout materials. These were worn over a shirt as a form of outergarment. Some were cut exactly like a regular shirt, only larger to accommodate layers and of heavier materials. They were often made of practical colors to be useful in working situations.
Trousers were typically made of a sturdy and longer-wearing material in the mid 19th century. Wool and linen were perhaps the most common, but jean-clothe, cottons, and blends of these materials were also worn. The fineness of the fabric would depend on the socio-economic standing of the owner, as well as what activities he planned to do in them.
These fabrics could be a plain in a solid color, or made of a plaid or check pattern. Once again, fabric selection would have depended on the intended use for the wearer. Patterns were frequently found on more informal trousers, while fine solid colors on dressy clothes, and hard-wearing solids on work clothes, but there is a lot of variation in between.