There’s not a single definition of what a “smartphone” actually is. However, most tech historians consider the IBM Simon to be the very first smartphone:
It was developed by IBM in 1994 and was the first device to combine a mobile phone with PDA-like features. A concept model was shown off at COMDEX in 1993 and generated a lot of interest, even making the front page of USA Today’s “Money” section the next day. The device allowed users to make phone calls, send and receive faxes, emails and pages and had comprehensive address book and calendar features. It lacked a dedicated number pad, relying instead on a touch screen interface. Perhaps most amazingly of all, the device was able to do all this using DOS!
BellSouth got an exclusive for the device, and sold it for $899 with a two-year contract ($1,305 adjusted for inflation) or $1,099 without a contract ($1,595). The carrier sold 50,000 units before discontinuing the phone in February 1995.
But the funniest thing about it was that it was the first phone to come with the ability to run third-party apps. An Atlanta company called PDA Dimensions developed “DispatchIt”, the only app ever developed for the platform. The app required a desktop PC client ($2,999) and a phone client ($299). Adjusted for inflation, the desktop client and one Simon client would cost $4,788 today! Not surprisingly, PDA Dimensions sold exactly two copies of the software.