LinusTorvalds released his first LinuxDistribution in 1991. This consisted of just two floppy disks, called "boot" and "root"; the first was the boot disk, which then asked you to put in the second one, which was mounted as the root filesystem.
This was quickly picked up and expanded by groups at Manchester University, Texas A&M University and others. The most popular early distro was SLS (SoftLanding? Systems), which had no PackageManagement to speak of; instead, all software components were built as part of a single monolithic installation. The problems with this led Ian Murdock to found the Debian project in 1994. RedHat was also started the same year. Many others soon followed.