This picture is an example of a fancy dress that would have been worn during the Civil War era (1861-1865). This particular dress is made of linen, so it would have been cooler than some of the other materials. An upper society woman in the north or south, and perhaps even the west, would have worn dresses similar to this one.
The undergarments beneath the dress were called “under pinnings,” and included bloomers, a chemise, corset, stockings and garters, petticoats, and a hoop skirt. The hoop skirt is what provides the billowing fullness of the lower skirt.
As was typical for the day, a woman would have worn gloves covering her hands made of netting (as shown here) or made from various types of leather. Sometimes they were fingerless. A woman never was seen in public without some sort of gloves. The bonnet, reticule, and parasol completed the outfit.
In the western wilderness of Arizona, this type of clothing would likely not be seen outside of major populated towns. My character Julia Colter, in A Heart Renewed, may have worn something like this on her father’s ranch in Texas.