The bra was not invented on November 3, 1914. Women have been binding and otherwise supporting their breasts for, literally, ages; the first bras may well date back to ancient Greece, where women would wrap bands of fabric across their chests, tying or pinning them in the back. And the "brassiere," as a widespread concept—the word comes from the French for "upper arm"—is generally thought to have originated with the DeBevoise Company, which used the term in advertisements for its whale-bone-supported camisoles. (French, then as now, had a certain je ne sais quoi with English-speaking consumers.) Vogue began talking about brassieres in 1907; in 1911, the word merited an entry in the Oxford English Dictionary.
But the bra—the garment that lifts and separates, via cups and straps—became part of the world, officially, on November 3, 1914. That was the day the United States Patent and Trademark Office granted a patent to Mary Phelps Jacobs for the garment she called a "brassiere."
The necessity that drove Jacobs's invention came down, in this case, to the fashion trends of early-20th-century America. The dresses of the time were cut for slim and boyish figures; they featured, on top of that, plunging necklines. This combination was, for the well-endowed Jacobs, awkward. While preparing for a Manhattan debutante ball in 1913, the 19-year-old became frustrated. Not only was the sleekness of her sheer evening gown compromised by her bulky corset; the undergarment also had a pesky way of rejecting the "under" aspect of things. "The eyelet embroidery of my corset-cover kept peeping through the roses around my bosom," Jacobs recalled in her autobiography, The Passionate Years.