This is a so-called "stamped envelope." It is Scott #U115a dark blue 1c Franklin, on what looks like cream paper, issued 1874-1886. It is called an "entire", which means you have the stamp on the entire envelope, as opposed to a "cut square" which is the cutoff corner of the envelope containing the stamp. Entires are worth more than cut squares, and your #U115a entire in used condition catalogs at $20.00. The address looks like it is to Leicester National Quarry, Leicester, Massachusetts. Leicester
is a small town in central Massachusetts which was an important manufacturing site in 1885. At the time Leicester's mills produced one-third of American hand and machine cards, which were tools for straightening fibers before spinning thread and weaving cloth.