jan 1, 1971 - Floppy Disc
The diskette, or floppy disc, was invented by IBM and in common use from the mid-1970s to late 1990s. The first floppy disk, introduced in 1971, had a capacity of 79.7 kB, and was read-only. A read-write version came a year later. The original cost was around $20.
Added to timeline:
Some early storage devices, to more up-to-date ones.