You can find some examples of women wearing bifurcated garments (pants/trousers/breeches) in the 18th century, but they are VERY unusual. Marie Antoinette had her portrait painted astride, likely inspired by Catherine the Greats similar portrait. They were both doing so in imagery of commanding their army, though both were still scandalous. Other examples are for practical reasons, such as Welsh coal mining women who climb through the tunnels and cannot wear petticoats. In general, petticoats do not hamper womens ability to work, so they aren't much of a problem.

One of the first pushes towards women wearing trousers comes from Amelia Bloomer in the 1850s (she didn't invent them, just popularize them). The bloomer suit or costume strongly resembles a style of Turkish costume that was very popular with European women for portraits or masquerade even back into the 17th century. These early costumes were still worn with skirted garments over the very loose trousers. When the bicycle gains popularity in the later part of the century, we see cycling ensembles of jacket and large trousers. These are still ridiculed and certainly not for the mundane dresser. In the early 20th century we find outliers wearing more masculine attire, such as Marlene Dietrich. There's also a craze for Turkish trousers in the 1910s and "pajama" bottoms in the 1930s. With WWII, more women are entering the industrial workplace and need practical garments for it. These trousers never really leave the woman's closet after this point. In the 1950s, it's socially acceptable to wear trousers in very casual circumstances, such as at the beach or for sporting attire. It's at this point as well that the trousers stop being only extremely loose-legged and can be found more fitted to the body. Something made possible not only through the gradual acceptance of that garment and fashion, but the adjustments in underwear and feminine products allowing for them to be worn regularly. Loose, short-like knickers would not do well in a pair of skinny jeans. Over time trousers become less and less a casual only garment for women, and now are acceptable in almost any situation. Many schools in the US still required girls to wear skirts into the 1970s (and some beyond).