The 1920's was a complex time in history and a time when the modern world began to take shape. Often referred to as the Jazz age because that is when Jazz music was first introduced to the world. Jazz is one of America's most important contributions to music. The free flowing style of jazz music also lent itself to a new fashion expression that took form around the same time in response to historical events.
Aesthetic
Art Deco was the main aesthetic of the time, influenced by geometric shapes, cubism and bold lines. It influenced all design at the time and especially fashion. The combination of black, gold and metallics defined the look with luxurious fabrics and exotic materials. We will see Art Deco Revival in the late 60's and early 70's in fashion.
Modernity
At the beginning of 1920's, the world was recovering from WWI as well as the end of the Spanish Flu. During those traumatic times, women stepped up on the homefront to help work where there were shortages in the workforce as well to volunteer as nurses for the sick or wounded. Additionally, the Spanish flu caused the life expectancy of 54 to fall by 12 years to just 48 years old. This then led to Prohibition to try and clean things up. The U.S. alone lost almost 1 million people between the war and the Spanish Flu in just a few years. Once the war and the flu were over, faced with mortality, people truly wanted to seize the day. The optimistic feeling that began in the 20's of starting anew spawned a great deal of innovation in music and fashion as well as many other areas in society. 
Rebellion
Embracing Jazz became a way of rebelling against social norms of the day. Women began to show their arms more and for the very first time they also showed their legs with dresses that went to the knee or mid calf. The dresses became more form fitting and took on a more sexy feel. Women began to smoke in public which was once against the law. Some thought all this led to promiscuity and decline in values.
Suffrage Movement
When women won the right to vote in 1918, it revolutionized their place in the world. They began to feel more and more equal to their male counterparts. This hard fought battle began to embolden women to be more bold in their appearance in the 1920's. Elements of these looks pop again in 60's fashion with the drop waistline.
Literature
la garconne, the French novel, had a huge influence on the style in the 20's. The book tells the story of a woman who finds out her fiancée is cheating on her. So in response to this devastating realization, she flees her bourgeoisie Parisian lifestyle. She rebels by cutting off her long hair for a styled bob, the most anti-feminine thing you could do at the time. She begins to wear men's clothing mixed with glamourous styles while out in the clubs at night living a risque lifestyle. Her look becomes known as the La Garconne style. This became the most adapted look of the 20's and into the 30's. Women apparently related to the main character, Monique's paralyzing pain and turning towards a non-traditional life, women followed suit and cut their hair off into the Eton crop or wore it up to look short. Cloche hats that fit snug to the head kept their feminine hair tucked away. Their makeup took a sad look with sloping downward eyebrows. In the story, Monique finds that she enjoys the freedom of her fashion choices as opposed to the expected styles put upon her previous life. La Garconne translated to The Bachelor girl.
Flappers
Flapper girls developed from la garconne and were really just group of young women who lived freely, were deemed wild and promiscuous in certain areas. Some of them frequented speakeasys during prohibition and were hanging out with bimbo men, doing cocaine and getting wasted all the time. Sort of a lost crowd. But their style left a lasting impression on history. The term Flapper became more broadly used to refer to the style.
The End of the Jazz Age
All this partying is portrayed as a fun time in history with happy dancing people but the dark side was starting to show up as decadence can get boring without something of substance to balance it out. As the decade winds down, there are large increases in crime, arrests for prostitution and public drunkenness. Prohibition divided the country. Additionally, the decade come to a less than celebratory end on Black Tuesday, October 29, 1929, when the stock market crashed after a period of a slowing economy and fear over what might lie ahead.
Although the fashions of the 20s subsided with the Great Depression, Jazz Music evolved and remained strong for another 25+ years. One of the most interesting times in music and fashion. 1920's vintage fashion illustrations available in store.