1784 - 1821: From kinda floofy to more streamlined.
1822 - 1850: Gettin' floofier.
1850 - 1866: BRACE FOR MAXIMUM FLOOF
1867 - 1874: Much less floofy, but with a shelf at the small of the back
1875 - 1882: OK, lose the shelf
1883 - 1887: What the hell, bring the shelf back
1888 - 1896: The Incredible Growing Shoulder Pads
1897 - 1910: Raise High The Waistline
1911 - 1929: How about we raise the hem slowly off the floor?
1930 - 1935: Nah, drop it again.
1936 - 1946: Wait bring it up again.
1947 - 1953: Add pleats, too.
1954 - 1957: You know what? Floof it again.
1958 - 1959: On second thought, no.
1960: Actually yes.
1961 - 1964: Yeah lose the floof. But bring the hem up.
1965 - 1969: Bring it up ever higher, until we have a tunic.
1970: BOOM, PANTS! There, we're done here.
No matter what era you lived in, the latest fashions tended to be set in motion by a class of celebrity trendsetters, notably royalty, later followed by wealthy high society, and eventually movie and TV stars. Women's fashions went through a paradigm shift in the early 20th century, when "freedom of movement" took hold and never again died out. Thanks goodness for that. -via Metafilter