I recently read a book called Uncommon Grounds about the history of coffee, and while I enjoyed it, I felt that the book History of the World In Six Glasses, was much more detailed in the earlier parts of coffee history, such as the 1200s-1800s, whereas Uncommon Grounds went over this, but went over the 1800s-now a lot more.
Then I realized, aside from a handful of books (most which I read) there aren't many sources for the history of coffee. Where does anyone get this kind of information?
I'd imagine combing through all books on any period in history, scouring them for any trace of coffee related things would take far too long. I'd also imagine that there isn't a depository of all texts and images related to coffee from any time period. So where would one go to get any of this, or any kind of really specific information?
There are many archives. They all serve as repositories of non book type sources of information (though some include books). When historians are writing a new book once they have reviewed the existing books (and journals) archives are where we turn.
Archives come in many flavors some of the most common are personal collections. These are archives built around the saved papers of one person. Often these become enlarged and contain many other works. Corporate archives are also common. These compile the records of certain companies or industries together. IBM for example no doubt has internal archives. Military collections are similar. There are also regional archives that collect material based on the area near the archives. Many collections are something of a mix of these things as well, containing information on many subjects.
Related to archives are internal files kept by companies and governments. The registrar of deeds is probably the most likely for a non-specialist to have come into contact with. Similarly historic associations and museums will keep collections of grey literature. The NC Underwater Archaeology Branch for example contains an extensive filing system on all known wrecks in NC waters. The US Coast Guard has a collection of their wreck reports stored in Atlanta.
Once you actually find the archive (which I will use generally to mean any repository here) materials are generally grouped by source and type. All the files from one author may be grouped together for example. Within that collection all the photographs are likely in one box and the letters in another. These kinds of division are made so that like in a card catalog things can be located easily, hopefully.
Most of the time you won't be able to go back in the stacks like a library. You will go through the catalog of the archive and tell the archivist what you want to look at. They will then pull those items for you and give you any special instructions for them. When you're done you put everything back and return the box to the archivist.
To use coffee as a specific example here's one way to go about it. First check and see if there is a large coffee importer in the area. Check and see if they existed at the time, if not did they have a parent company? Assume for this case that neither of these are true. In this case ask where the coffee was imported. Go to that port and check the archives. Did a packager exist in the area to make the coffee ready for sale in the city? For transport to other cities? Does a collection of bills of lading exist from which the amount of coffee being imported can be calculated? Tax records on imports? News paper articles advertising wholesale lots for auction? So on and so forth. Primary source research is a real rabbit hole where you never quite know where you are going to end up.
There often actually are very specific collections available, on specific subjects. For example, the place the titanic was built. The biggest local library near there is likely to have gathered a lot of material on that, including newspapers and such.
Then theres the good old physical paperwork from back in the day. The ships bringing in the coffee would have manifestos saying how much they brought in and where from. The captains would keep a diary too. Plantation owners as well.
But yeah as you said, tracking all that down can be a pain. Public collections like libraries and archives are usually your best bet. I dont know where you're at, but around here librarians jump for joy when they see somebody thats actually interested in books these days. Theyre extremely helpful, often giving addresses and events to try and help you out.