Many assume that typewriters have always had a key to go back one space, to add a missed character, or perhaps to strike an error. However it was many years before the backspace became mainstream.
Pre-1900 very few typewriters had a backspace key, notably the Burns typewriter, photo courtesy of Tony Casillo. This was likely added by the sales office or as an aftermarket device.
It wasn’t until around 1906 that companies like Blickensderfer, Densmore, Remington, and others got on the backspace bandwagon. Finding out who was the first is very difficult because machines got upgraded all the time. It helps that we can look back and at least see where it’s not present, such as on the Jewett, Sun #2, early Blickensderfer’s and Hammond’s, Franklin, Densmore, and Fox.
The Hammond Typewriter company, for its part, debuted an optional “add on” backspace key for the No. 12 in 1906. This came in the form of an iron-casted bracket that affixed to the rear-right of the frame.
The key, a simple lever action, pushed a hook up, catching on the carriage rail, and pushing it back one space.
The backspace key was so popular that the company made it a standard feature the following year.