RMS Titanic sank in the Atlantic ocean after striking an iceberg. Call me silly, but it seems like it would have been a lot longer ago than a hundred years. I guess it just seems that way because I wasn't alive when it happened? Who knows.
Anyway, I bet you are wondering how I tie this into letter writing right? Well, did you know that 5 experienced postal clerks (three Americans and two Britons) served on board the Titanic? I didn't either. To be honest, I never thought about it before. Well, the RMS in the Titanic's name stands for Royal Mail Ship. And having that designation meant that the ship was carrying mail for the Royal Mail and the USPS. Wikipedia's entry for the Titanic says that just under 27,000 cubic ft were designated for storing mail, both letters and parcels as well as specie (coins and bullion).
When the ship went down most all of the mail was lost. That includes 3,423 sacks of mail! All told that would average about 7 million pieces of mail, including an estimated 1.6 million registered letters and packages. The National Postal Museum also estimates that around $150,000 dollars (which was a lot of money in 1912) worth of international money orders sank with the Titanic. Leaving a huge mess to clean up in the end.
Because the Titanic is in international waters, it is technically salvageable. Meaning that if you or I wanted to, we could dive down and grab a piece of Titanic for ourselves. However, some institutions, like the Smithsonian prohibit displaying relics from such disasters because of a 'sanctuary principle'. Basically, they want to respect the site. After all, it is the final resting place for 1,514 people. But incase you were curious, if ever a bag of mail was salvaged from the wreckage, the USPS would attempt to deliver any readable mail. Which is a nice thought.