Something people often skip, but I’ve found insanely simple and useful, is reading newspaper articles released in the area and during the period in which you’re writing. That doesn’t just give you information on what their writing, word choice, and general linguistic styles look like, it also gives you information on what the people’s general mindset was like, what things were trending or popular, what kinds of issues were arising, etc. etc. and can give you a wealth of context in order to build a more realistic and accurate depiction of the era.
Local libraries generally keep archives, otherwise you can easily read them online through sites like the Library of Congress website.