I am writing my dissertation on John Steinbeck's female characters. Fortunately for me, Steinbeck was a prolific letter-writer. He typically wrote between six and eight letters every day. Most letters were multiple pages long, and the majority were hand-written. He wrote to his wives (of which there were three), his editors, and friends (esp Ed Ricketts, the marine biologist who was his closest friend and who the character of "Doc" in Cannery Row is modeled closely after). He rejoiced in good times, documented the bad times, wrote extensively and eloquently about his craft, and about his relationships with the people in his life. Remarkably, almost everyone kept his voluminous correspondence. It took me four trips of two weeks each, going to the Special Collections archives at Stanford University to go through them all. I was in the library from the second they opened until the second they closed.
His personal correspondence helped me understand Steinbeck and his characters in ways I would never have been able to otherwise. His tumultuous relationship with his second wife, Gwyn, is mirrored in his novel East of Eden (she is most definitely Cathy). His ideas about maternal feminism are deftly employed in the character of Ma Joad. I could go on and on.
Another wonderful example of the value of letter writing is the collected correspondence between the historian Shelby Foote and the author Walker Percy. The two were lifelong friends and maintained a lifelong letter-writing exchange. The letters reveal two writers at their craft, the ups-and-downs of success and failure and personal insights that shed light on their areas of expertise. Mr. Foote is now in his eighties and Percy passed away in 1990. About ten years ago, I attended one of Foote's lectures. Even ten years after the death of his close friend, you could tell how much he missed getting those letters from Percy. His voice wavered as he recounted how they relied upon one another in this almost-lost art of letter writing.
In our age of dispoable IMs and ephemeral email, scholars of the future are unlikely to know what goes on behind-the-scenes in a writer's mind. This saddens me.
There are efforts underway, however, to bottle some of our technological vapors. Although this project isn't strictly letter-based, the efforts of the NPR project "Storycorps" works in a similar fashion as a letter. In private sound booths, two people enter to tell one another about some aspect of their lives. Since 2003, Storycorps has collected over 70,000 stories of people around the country. It reminds me of a line from James Frazier's novel, Cold Mountain: "There wasn't anything to her story, save it was her own." We all have a story to tell.
My grandmother (born in 1888) used to save all of her correspondence. As a child, I used to read them all, especially the postcards she received from friends and relatives that were postmarked from all over the world. I was enthralled with the pictures and information received from seemingly mundane events in various cities and tourist attractions. Of particular interest were letters from her sister--my great-aunt--who often traveled to Warm Springs, Georgia for treatment in the waters for her tuberculosis. Several of the letters mentioned the appearances of President Franklin Roosevelt, who vacationed there at "the Little White House," where he also soaked himself in the hopes of soothing his own body. The letters revealed my great-aunts hopes and worries concerning her illness, which eventually killed her. She died before I was born, but I still have memories and some knowledge of her--solely from the postcards that she had mailed to my grandmother.
There are at least two ways to answer this, depending on whose letters you are reading.
First, if you read the letters of "important" people, like the letters between John Adams and his wife Abigail, you learn things about what these important figures knew and/or thought about at important points in history. That is why we know, for example, that Abigail Adams asked John Adams to give women rights (during the writing of the Constitution) and we know why John Adams thought that was a bad idea.
Second, if you read letters of ordinary people, you get more of an insight into the lives of everyday people. Historians today think that it is important to know how everyday people exprienced events, not just what the leaders said or thought. The letters of common people give us more insight into things like how, for example, immigrants experienced their new lives in the US or how soldiers experienced WWII. These things are important, especially in the eyes of modern historians.