Not just a stack of old letters...
A few years ago, the state of Virginia asked its residents to share old letters, diaries, photos, etc., that families had kept from the Civil War. Two librarians went around the state scanning items people were willing to provide. Over five years they scanned over 33,000 items (!) which are now publicly available online at the Library of Virginia.
This is a perfect example of the incredible power of history viewed through individual story-telling. I encourage you to read the moving write-up in the Washington Post, from which the photo above is pulled (photo credit: Library of Virginia). Both the state’s undertaking and the substance of the documentation deserve attention.
So how does this relate to you? If you’re hesitating about what to do with old family letters -- and they don’t have to be 150 years old -- don’t dismiss them yet. It’s very possible your state archives, local library or historical society may want them. Institutions like this collect materials for their archives (also called special collections) and someone on their staff will be able to explain what their collection requirements are.
If you can’t find an institutional home for your materials, don't give up. Consider scanning them yourself (or having them scanned) and keeping the originals in a safe place. You can then share these items with your family in digital form. Another option is to publish a book of these letters, along with photos and other scanned mementos, which ensures your family history is passed down to everyone in the next generation, not just the person whose attic will house these letters.