While many people think that Rolex invented the first automatic wristwatch, it was actually a different brand. John Harwood, a british watchmaker, patented the first automatic or selfwinding wristwatch in 1923. The first Harwoods went on sale in 1928. As far as I can find out, it was Fortis who actually produced about 30000 Harwood watches until 1931 when Harwood had to shut their business.
So here is a bit of history of the first automatic wristwatch. The early beginnings were not as glorious as some may think. In 1930 Rolex improved the automatic winding from a bumper to a selfwinding bidirectional rotor. A major improvement which kind of lasts up to today although there have been improvements over time.