You should definitely read up on your timeframe, and nonfiction books written by historians are your most authoritative source.
For books about clothing or fashion through the ages, browse GT375, GT575 and TT500-600. We have some sets in the Reference Collection on the Main Level of JFK, but if you want to check a book out, go to the Upper Level for the GTs and Lower Level for TTs. (What's the difference between GT and TT? GT books are more from a cultural anthropology lens, while the TTs are more from the fashion industry lens. Both will have images with examples through different time periods.)
Browse the GT2850s for books on the history and culture of food. There are two major print sets in the Reference Collection on the Main Level.
For more detailed guidance on researching historical settings, see Chapter 4 "Research" in Alan Rosenthal's From Chariots of Fire to the King's Speech: Writing Biopics and Docudramas (Southern Illinois University Press, 2014)
The subject headings aren't as useful here, because they aren't consistent. The one term that sometimes comes up in the subject headings that isn't obvious is correspondence. So add this string to your search:
(letters OR diar* OR autobiography OR memoir* OR correspondence OR "personal narratives") AND [person or type of person]
If I wanted books with primary accounts of Chinese immigrants, I'd search (I am in the Advanced Search):
(letters OR diar* OR autobiography OR memoir* OR correspondence OR "personal narratives") chinese immigrants
Digitized and Archival collections
There are tons of primary source materials that have been digitized and can be found on the web. The trick is locating them in amongst all the other websites in a Google search. As with any Google search, the more specific you can be, the easier to find.
Most of the collections are going to be found in Archives or Special Collections of libraries (both university and public libraries) and in historical societies and museums. The traditional method for archives to promote their holdings is through describing the content in finding aids. ArchiveGrid is a searchable catalog of over 5 million records from over 1,000 archives. The collections may or may not be digitized.
But lots of archival materials haven't been digitized, nor have their collections been included in ArchiveGrid. This is where it gets interesting! If you have found some really good historical or nonfiction, academic books on your topic, look through the references and see if they discuss where they found archival material. Otherwise, I would suggest narrowing your geography to a particular city and see what archives are in the area. The Society of American Archivists maintains a directory by city. Call them and find out whether they have anything relevant.
Visiting an Archives in Person or Requesting Materials
If you know the name of the archive that has relevant materials, but you've exhausted what has been digitized, go to the About Us or Visit Us part and note what restrictions they place. Many have limited hours and staff, and a few are picky about who they let in. (You may have to email asking for permission and justify your need.)
You may be able to get copies of the relevant materials sent to you. Policies vary from archive to archive, so see what they say on the website, or call them.
For more detailed information about using archives, see Using Archives: A Guide to Effective Research from the Society of American Archivists.