Panties as a Feminist Statement

Amelia Bloomer was a strong advocate of the 19th century women's movement and the editor of a reform newspaper known as The Lily (Garber 1997 [1992], 314). Bloomer's name will remain in history for a garment that she and Elizabeth Cady Stanton, another member of the reform movement, first wore in 1851 in Seneca Falls, New York. Although the garment was invented by Elizabeth Smith Miller (another women's rights advocate), it is forever associated with Bloomer (Ewing 1978, 63). The garment is mostly simply described as a knee-length dress over a pair of caftan-style pants, inspired by the Orientalist movement.

... Women's trousers, and the wide-spread use of bifurcated garments (what led to modern-day panties) for women in general, did not re-surface on a wide scale until the end of the nineteenth century. What really launched the second wave of bifurcated garments into the limelight, not only as underwear but also as outerwear (in the form of trousers or split skirts) was something completely unrelated to fashion and politics—the invention of the bicycle. Although the bicycle was first invented by Karl von Drais in 1817, it did not gain widespread popularity until the late 1870s and early 1880s (Oddy 1996, 60). Even so, it was most popular among men. In fact, the technology of the first bicycles (specifically the placement of the cranks and pedals) was such that it was nearly impossible to ride the bicycle with a long skirt (Oddy, 61). In the 1890s bicycles for men and women emerged, while at the same time, trousers were also gaining popularity as a "sport" dress to accommodate women who rode both women's and men's bicycles (Oddy, 64-5).

Source: http://www.jolique.com/undergarments/bloomers%20_and_bicycles.htm