As the proverbial question of who "wears the pants" in a relationship suggests, the history of women's pants says as much about the evolution of twentieth century gender roles as it does about the capricious swings of the fashion pendulum. Pants for women emerged from the burgeoning nineteenth century feminist movement, which demanded a change from Victorian dresses to a more practical costume that would permit women to engage in activities beyond those traditionally assigned to the female domestic sphere. Ironically, however, women's pants would achieve widespread social acceptance only when the fashion industry convinced women that pants were a necessary part of a well-dressed woman's wardrobe.

The first feminine garments approximating pants were "bloomers"—a full skirt reaching just below the knee, with full-cut trousers underneath. Named for their chief advocate, feminist Amelia Jenks Bloomer, the outfit liberated women from heavy skirts, whalebone corsets, petticoats, bustles, and padding. In spite of the unprecedented mobility bloomers permitted, the fashion never spread beyond a small group. The bloomers' association with the suffrage movement stigmatized its wearers and, as an article in the September 1851 issue of Godey's Lady's Book hypothesized, bloomers did not take because most women would not wear what did not originate in fashionable Paris.

Though unsuccessful themselves, bloomers influenced the design of the popular feminine bicycling costume of the 1880s and 1890s. The outfit, consisting of a pair of knee-length, very baggy knickerbockers, had a split skirt with stockings worn beneath. These bicycle bloomers marked the first concession made by the fashion industry towards enabling women's participation in skirt-prohibitive activities. Formerly, as with the original bloomers, an activity was deemed immodest and unladylike if it could not be performed in a skirt. While some criticized bicycling for this reason, most women showed no inclination to give up cycling, and the craze for bicycle bloomers raged for the next two decades.

As the somber mood of the World War I replaced the frivolity of the "Gay Nineties," women replaced men in the factories the latter had abandoned for battlefields. At work, when skirts proved too cumbersome, women wore trousers or overalls, although this practice was much criticized. Women worked in the fields too, sometimes wearing overalls, as noted by L.M. Montgomery in her book Rilla of Ingleside (1921) which depicts life on Prince Edward Island during World War I. In the novel, some young women wear pants as they work, while the older women working beside them remain in their skirts because pants were still considered indecent or shocking. Clearly, though, those women who wore pants during World War I did so for reasons of practicality and not of fashion.

Following the war, in the 1920s, women exposed their arms and legs, flattened their chests, bobbed their hair to look boyish, and got the vote; but pants remained taboo, except in the realm of sports. Here, ease of movement somewhat dictated fashion. And so the ski-costume, a knitted tunic over knitted trousers which fit into ankle-high ski boots, was created. Riding outfits similar to men's became popular, and women wore the loose trousers of "lounge pajamas" on the beach.

When diva film star Marlene Dietrich appeared in slacks with flared bottoms in her United States debut film Morocco in 1930, she signaled the emergence of women's pants from sportswear to high fashion. Wearing them both in films and private life, she popularized the pants look. For summer wear, shorts and beach slacks were stylish, and pants were worn regularly with short-sleeved knit tops. Women's pants had gained such importance by 1939 that in the November issue of Vogue the magazine advised, "Your wardrobe is not complete without a pair or two of the superbly tailored slacks of 1939."

During World War II, however, fashion followed the needs of the war. Clothing was simple, sensible, and, in some cases, rationed. In England, the Board of Trade specified the maximum amount of cloth and buttons which could be used in women's slacks. Urged by images like "Rosie the Riveter," shown once on the cover of The Saturday Evening Post in 1943 as muscular and wearing coveralls, women returned to factory work; this time they wore their dungarees without looks askance.

In 1947, after the austerity of the war years, Christian Dior introduced his lush New Look, reverting to full skirts and soft femininity. Women's pants, however, were by then an acknowledged fact, and the 1950s brought many innovations to casual wear. Women wore a variety of slacks, ranging from tight-fitting to loose, worn with all types of blouses. Following the post-World War II baby boom, the 1950s ushered in the cult of youth and the creation of a market division specifically for teenage fashions. Girls wore Capri pants, stretch pants with stirrups, and Bermuda shorts.

These innovations set the stage for "unisex" fashions, which were developed in the 1960s. Both men and women wore blue jeans, "hipsters" and close fitting pants with zip fly fronts. The spirit of this latest association of pants with social and sexual liberation can be seen in Alice Walker's novel The Color Purple (1982), in which the social victory of the heroine culminates in her opening of a unisex jeans shop. In addition to jeans, pant-suits became popular with women in fabrics ranging from PVC and lurex to velvet and satin.

Since the 1960s, women's pants have run the gamut of trends from the bell-bottoms of the 1970s and the skin-tight jeans of the 1980s, to the return of bell-bottoms and tight jeans in the 1990s. The fashion, however, is not yet entirely divorced from its controversial beginnings. Only in the 1990s has the issue over whether women should wear pants in the workplace cooled, aided by the phenomenon of "business casual" days. Perhaps a greater indicator of the merge in the feminist and fashionable aspect of women's pants is reflected in the 1998 Miss America Pageant, where a number of the contestants, having been allowed, for the first time, to choose their outfits for the introductory number, came out wearing jeans.