World War I helped popularize the modern bra.
For nearly 400 years, women in Western Europe and North America were expected to wear corsets beneath their clothing — restrictive, binding bustiers that cinched at the waist and opened toward the chest to accentuate the natural curves of the body. This all changed around the First World War, when a shortage of metal, the dominant material in corsets, led to a redistribution of resources as well as a cultural shift. Steel went toward planes and tanks and other military equipment, and American women went to work in factories to contribute to the war effort. Hard labor, however, could not be performed in a corset — indeed almost nothing could be performed in a corset, barring sitting and standing. These women needed something breathable, loose, and functional.
Enter Caresse Crosby, a young debutant who, in lieu of wearing a corset, opted to sew together two handkerchiefs ahead of a social ball, debuting the first “modern bra” on the dance floor. She patented the first-ever “backless brassiere,” which she later sold to the Warner Brothers Corset Company. From there, the modern bra took off in a variety of styles and functionalities. In the postwar era, the bandeau bra — a cylindrical, cupless garment not unlike a modern bralette — was popular under slim-fitting 1920s dresses. Soon after, the cupped bra took shape with its infamous pointed cups and letter-based sizing. The variable styles allowed women the chance to express themselves and move their bodies freely, though the relief of taking off a bra at the end of the day is universal and timeless.
https://historyfacts.com/world-history/fact/world-war-i-helped-popularize-the-modern-bra/
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I never wear a real bra anymore, can't imagine having to wear a corset, something that restricts your breathing, compressed abdominal organs, could cause poor digestion and over time the back muscles could atrophy. In fact, long term tight lacing led to the rib cage becoming deformed.
A camisole or sports bra is fine with me.
Thank the goddess for a shortage of metal.
I want to be Free!
= new reply since forum marked as read
The way the leaves were positioned, the first thing I saw before I moved the plant out of the way was a thread authored by you called, "I helped popularize the modern bra."
Yep. That was me! I did that. 
With people insisting that if they're fitted correctly, they aren't that bad, whatevs.
As for the "letter-based sizing", I have often jokes that batteries and bras are sized roughly the same. 
