Are you ready? Alright, here we go:
What the Victorians knew as the “sack” coat first appeared in France at the end of the 1840s and quickly spread to England and America, becoming very popular in the Eastern United States by the mid-1850s.
Originally intended for extremely informal occasions, sack coats soon became working and business wear for skilled workers and clerks across America. By the end of the 1850s, the U.S. Army had adopted a military version of the sack coat as fatigue wear. By the 1870s, sacks were being worn as general purpose outdoor and working jackets by many Americans, particularly outside of the East.
Despite what you may have read, they are not called “sack coats” because they are oversized, loose, or otherwise fit like a sack, nor is it because there is no “front dart.” Sack, sac, sacque, etc. all refer to the way the back (not the front) of the jacket is cut; i.e. “sack cut.” This simply means the back is formed of two pieces only, cut relatively straight down, instead of being made up of four curved pieces with hidden pockets in the tails as on more formal and traditional coats, such as tail coats, morning coats, and frocks.
Some tailoring manuals of the 1850s and 1860s refer to the sack coat by other names, but they are all the same garment. Length of skirt and sleeve, number and style of pockets, collar, lapels, and the cut of the front skirt were the elements of changing style in the sack coat from 1850 to 1900. At all times in that period, sack coats were diverse and made in “close cut,” “full cut,” “single breasted,” and “double breasted” versions.
In 1900, Brooks Brothers introduced its “No. 1 Sack Suit.” This version of the sack became the iconic ready-to-wear model of the American upper class version of the English lounge suit. It was a basis for the collegiate (“ivy,” if you prefer) style variants of other multi-store makers like Chipp and Press, as well as all the individual boutique shops—often adjacent to elite colleges and prep schools—that serviced the social groups wearing this look.
Following World War II and through the 1960s, the combined forces of the GI Bill and the widening enfranchisement of new groups into American collegiate life entwined this look with American confidence and optimism. The style became an element in a shared sense of destiny among social classes that had been more openly divided in the past.
So, many wore it: from prep school boys to corporate kings to Presidents to jazz musicians and hipsters.
Today, it is largely the preserve of the dwindling ranks of men who wore it originally and of mid-century clothing re-enactors. Maybe sprinkle a few Southerners in.