Is there an online (preferably free) archive with letters written by people in the past? (other written material which reflects the era from the point of view of someone who lives in it will also be acceptable)
closed as off topic by coleopterist, Mark C. Wallace, Luke, lins314159, Steven Drennon♦ Feb 13 at 12:38
Questions on History Stack Exchange are expected to relate to history within the scope defined in the FAQ. Consider editing the question or leaving comments for improvement if you believe the question can be reworded to fit within the scope. Read more about closed questions here.
There are some letter archives from WWI:
As another example, you can read the letters of Cicero.