Before email 1: before envelopes --- 1855
Instead of envelopes, one could use a folded sheet of paper. Sometimes, the back was used for writing, but in this case it is blank. This was sent from Boston, Massachusetts (USA) to Lowell, Massachusetts on August 25, 1855. The red mark on the bottom is sealing wax and the hole at the top is where the paper was torn when opening it.