With a new version OS X 10.10 named Yosemite soon upon us, I remembered back to the first version that was released in March of 2001. Actually there was a server version in 1999 that I never used. Yosemite is 11th version for the desktop since the first was 10.0. I still have a copy of OS X 10.0, code named Cheetah though the box did not have the cat name on it. That version cost me $129.
In version 10.1 Apple formally used the name Puma. They continued with big cat names until 10.9 which they named Mavericks. I have copies of all and actually run 10.3 Panther, 10.4 Tiger, 10.5 Leopard and 10.6 Snow Leopard on various old Macs in my collection. Tiger supports OS 9 in Classic mode as well. You can read about all versions of the Mac OS at: http://en.wikipedia.org/wiki/History_of_Mac_OS
I am also in the process os scanning all old Mini’app’les newsletters to add to our web site. It appears that the first substantial mention of OS X was in the May 2001 issue where an article from Tidbits was included. Since an OCR of the scan copy required cleanup, I looked on the Tidbits site to find the original. Not finding it, I emailed Adam Engst, the author, who provided the following link: http://tidbits.com/article/6372 . This article still has good advice as to who should install a new version of Mac OS X and when.
If you plan to upgrade to Yosemite, the following is a good resource though there are plenty of other free articles being published.