On October 23, 1999, Apple released OS 9 (codename: Sonata), and I have fond memories (well, memories) of trucking over to my college bookstore and picking up a copy. I even remember that the cover of the box was green.
Some of the new features introduced in OS 9 included the introduction of automatic system software updates via the control panel (which continues on to this day), CD burning, Keychain password storage, Sherlock 2, and the addition of the “Window” menu to the Finder. It’s kind of mind boggling to think about, but OS 9 also enabled the Mac to finally support files over 2GB. Man, talking about coming a long ass way in 10 years – and it makes you wonder what feature of today we’ll be laughing at in 2019.
Interestingly, Apple still has a support page up for OS 9.