In the nineteen teens, the silhouette of what women wore looked a lot like this:
Fashion historians are always going on about what was happening socially defined what people wore. Sometimes they're full of it, but in this case, they were spot on.
Women were fighting for the right to vote here in the US, and getting more liberated all over the world. Check out these suffragists:
Sure, I'm a fashion geek, but whenever I think "right to vote", I think of these clothes. These were what the stylish, independent, badass woman was wearing in the 1910s. (They were independent, but never thought to take off their hats... I wonder if that was a style concern, or a social one?)
One of the first things these independent, badass women did was ditch the corset. Since women had been wearing corsets for a century, no one was quite sure how to dress. Remember our old buddy Poiret? He was one of the first to jump on the no corset idea, and he did a better job of it than most:
Fortuny also worked in this era, giving the world the Delphos gown and loose jackets and capes:
But really, other than a few skilled designers, the bulk of women's clothing in this era was very obviously in transition, between the ruffles and fluff of the 1900s and the sleek glitz of the 1920s. Everyone seemed paranoid at the idea of someone getting a glimpse of an uncorseted breast or waist, and so they layered like crazy. No one's quite sure, but most historians think the bra didn't get invented until the 1920s, so this era was underlined (haha) but a lack of what we think of as proper undergarments. I guess this is kind of how we still dress, when not wearing a bra and worried about stray jiggles. (Don't we?)
Occasionally, you run across something sleeker and slimmer, but I suspect the sleek evening dresses had stays and boning sewn into the dress itself instead of a corset. Not much of a change, except in terminology. (We still do that. I've sewn stays into evening gowns, myself, when making them. These days we use plastic, but we're still using engineering to strap ourselves in.)
Remember, many of the women wearing these dresses were the same ones who'd been wearing corsets in the 1900s. If they grew up wearing corsets, they would have had small waists even after they took the corsets off.
And since we're enjoying the clothes, here are some coats from the same era: