On August 30th 1963, Philips launched the audio cassette to the world at the Berlin Audio show - the Funkausstellung. In the face of competition, Philips was very clever in giving other manufacturers a license to the recoding format free of charge. By 1966 over 250,000 recorders had been sold in the US alone and Japan soon became the major source of recorders. By 1968, 85 manufacturers had sold over 2.4 million players. There were ill-fated attempts by others, notably Sony, to try and make larger versions of the same thing so that they tape could move at double the speed for better fidelity (remember the elcaset).
In the end, the introduction of Dolby noise reduction meant the medium was good enough for portable use and sounded great in the car. Still have racks of cassettes on the wall in the studio...waiting for one day when I can consolidate the Media Network archive.
I also remember that Lou Josephs came up with a recording of DXing worldwide from WNYW, a shortwave radio station with studios in New York. We used it in a special show we made in 1992. I distinctly remember that the cassette took some time to break into the US market. Even in 1969, the presenter at WNYW didn't know how to pronounce it - he says kay-set. And the music choice didn't really start to compete until Dolby reduced the hiss. The tape inside the housing was running at a 4.75 cms/sec - so there wasn't much of a signal getting to the playback head.