Just thought I would make a quick note on how I search through the museum:
Go to the website and click on Search the Collections, which is under the collections category.
There will be tabs that say Who What Where When and In the Museum. Under What I click on Dresses. After that you can even click on What again and put in more specific textiles and materials. Under When I put in 1800-1900 (too bad you can't break it up at all). And sometimes I put in North American or English. French will also come up with similar styles, usually more extravagant.
Feast your eyes!