A union suit is a type of one-piece long underwear. Created in Utica, New York, United States, it originated as women's wear during the 19th-century United States clothing reform efforts, as an alternative to constricting garments, and soon gained popularity among men as well. The first union suit was patented in 1868 as "emancipation union under flannel". Traditionally made of red flannel with long arms and long legs, it buttoned up the front and had a button-up flap in the rear covering the buttocks (colloquially known as the "access hatch", "drop seat", "fireman's flap", and other names), allowing the wearer to eliminate bodily waste without removing the garment. Depending on the size, some union suits can have a dozen buttons on the front to be fastened through buttonholes from the neck down to the groin area.
The garment remained in common use in North America into the 20th century. As its popularity waned, it became chiefly working men's wear, increasingly replaced by two-piece long underwear, also known as "long johns". It was not uncommon until the mid-20th century for rural men to wear the same union suit continuously all week, or even all winter. Normally, no other type of underwear was worn with it.
Union suits are still commercially available, but because of their association with "old fashioned" usage, and presumedly "unsophisticated" rural wearers, they are considered comical. The rear flap is also associated with humor, and in film and television the appearance of a union suit, viewed from behind, is a form of mild toilet humor. The 1999 movie adaptation of The Wild Wild West, the TV series Rugrats, and the Family Guy episode "No Meals on Wheels" are among those that used the rear flap on union suits for comical effects.
The union suit makes an appearance in Louisa May Alcott's book Eight Cousins, as a preferred alternative to corsetry under the name 'Liberty Suit'. It also makes a presence in the 2003 film Cold Mountain. The union suit is referred to several times in Laura Ingalls Wilder's books about pioneer life during the mid-to-late 19th century in the United States, and in Harper Lee's book, To Kill A Mockingbird. In the expansion Undead Nightmare for the game Red Dead Redemption, the player begins play wearing a union suit and can choose to continue to wear it throughout the game, if desired.
In Britain, this garment has often been known as "combinations". When made from the traditional wool as recommended by Gustav Jäger, these are "woolly combinations"—sometimes abbreviated to "woolly coms".
See also 
- "Reforming Fashion, 1850–1914". The Historic Costume Collection. Ohio State University. Retrieved 2006-10-21.