In the spring of fifty years ago this year, work started on MIT's highly influential Compatible Time Sharing System. The system then was first demonstrated in November of that year. Some of you may be interested in a CTSS commemorative document that a couple of us of recently compiled; see item #5 at <http://www.computer.org/portal/web/volunteercenter/history>http://www.computer.org/portal/web/volunteercenter/history This commemorative document is intended to be popular overview of the history of CTSS, not a scholarly report. We may put out an update with new information we receive post initial publication. (We certainly will update the PDF to fix any typos that anyone spots.) If you have any comments on this document, perhaps send them off list to my email address below so other list members don't have to see messages in which they are not interested. Sincerely, Dave Walden dave.walden.family@gmail.com