Young Blonde Girl Strips Her White Underwear

By the end of the 1910s, Chalmers Knitting Company split the union suit into upper and lower sections, effectively inventing the modern undershirt and drawers. Women wore lacier versions of this basic duo known as the camisole and drawers.
In 1912, the US had its first professional underwear designer. Lindsay "Layneau" Boudreaux, a French immigrant, established the short-lived panty company Layneau. Though her company closed within one year, it had a significant impact on many levels. Boudreaux showed the world that an American woman could establish and run a company, and she also caused a revolution in the underwear industry. Boudreaux is possibly the reason why upscale underwear and panty stores exist today.
In 1913, a New York socialite named Mary Phelps Jacob changed women's fashion forever when she created the first brassiere by tying two handkerchiefs together with ribbon. Jacob's original intention was to cover the whalebone sticking out of her corset, which was visible through her sheer dress. Jacob began making brassieres for her family and friends, and news of the garment soon spread by word of mouth. By 1914, Jacob had a patent for her design and was marketing it throughout the US. Although women had worn brassiere-like garments in years past, Jacob's was the first to be successfully marketed and widely adopted.
By the end of the decade, trouser-like "bloomers", which were popularized by Amelia Jenks Bloomer (1818–1894) but invented by Elizabeth Smith Miller, gained popularity with the so-called Gibson Girls who enjoyed pursuits such as cycling and tennis. This new female athleticism helped push the corset out of style. The other major factor in the corset's demise was the fact that metal was globally in short supply during the First World War. Steel-laced corsets were dropped in favour of the brassiere.