What style of dress would a young lady living around Pennsylvania wear in 1880? I'm most particularly interested in what they wear UNDER their gown. And what a day dress would be like in comparison to what they'd wear in the evening.
You've come to the right place, Janelle! Here we go. Backwards. First up, a typical evening gown, from the most popular designer of the late 19th century (and my personal favorite) Charles Frederick Worth. He set the tone for fashion throughout this decade, especially for middle to upper class ladies. And living in Pennsylvania, your heroine certainly knows who Worth is.
This is one of his more subdued styles, but the decade didn't get crazy until after 1885, so it's a good typical example of an evening gown.
1880 is part of the transition from what's known as the sheath dress to the second bustle era. Yes, there were two, and each had a distinctive shape. I prefer the 1870's bustle myself, it's less severe.
It would have looked something like this one. Under this are the lady's drawers (also called pantalettes) and a petticoat. Then over the bustle cage there's one or two more petticoats, depending on the weight of fabric her skirt is made of. Showing one's bones was the height of rudeness. That's what the metal wires are called. And yes, it is possible to sit in this thing without killing yourself. It was done without thinking by the ladies who wore them.
Janelle also mentioned this was her first time writing a character who would wear actual fashion, instead of prairie type clothes. So, here are a couple of my favorite fashion resources. The first is Fashion-Era. It is one of the best sites out there for a general overview of 19th century and early 20th century fashion. She covers the silhouettes as well as the transition to each and has lots of illustrations.
The Holy Grail of fashion research is the Metropolitan Museum in NYC. Their website is HUGE. I mean HUGE. There are probably hundreds of thousands of dresses in their archives, and even though they're not on display they are on the website. It takes a little while to get the hang of searching and I'm still figuring it out. But for Janelle I suggest starting with "Bustle, 1880". You'll get a good range of results including the late 1870's through the end of the 1880's.
Welcome to the world of real historical fashion, Janelle! Be careful. It's addictive.