When I talk about the Nessa Donnelly mysteries as a "World of Secrets" it is partly because secrets were such a strong undercurrent to the Victorian Era. Technology, industry, immigration, economic inequity and social upheaval created an atmosphere ripe for the rise of Secret Societies.
The Knights of the Golden Circle were estimated to have over 400,000 members in Kentucky. I would like to think that nobody in my family belonged, but the odds are that someone somewhere in my family tree was a loyal member of the KGC. If not, there were the Regulators, the Klan, or some other secret society to besmirch the family tree (at least by our standards today.
The ground between the public and private worlds of men and women became unstable in the aftermath of the Civil War. Middle and upper-class men turned to secret Societies, fraternal orders, and private clubs as a way of holding on to some semblance of the social order they understood. This didn't exempt the lower classes: the Klan was particularly popular with working class white men who deeply resented newly freed men competing with them for jobs and housing. Through the secret societies, they hoped to regain the social position the war had taken from them.