SLS was the first release to offer a comprehensive Linux distribution containing more than the Linux kernel, GNU, and other basic utilities, including an implementation of the X Window System.
History
SLS was the most popular Linux distribution at the time, but it was considered to be rather buggy by its users. It was soon superseded by Slackware (which started as a cleanup of SLS by Patrick Volkerding) and Yggdrasil Linux/GNU/X, among others.
Similarly, Ian Murdock's frustration with SLS led him to create the Debian project.