FWIW, the oldest accessibility API was Microsoft Active Accessibility (MSAA), which was added to Windows 95 in a service pack in 1997. Classic MacOS never had an accessibility API; the Outspoken screen reader for that OS had to rely exclusively on ugly hacks (e.g. patching Toolbox functions). OS X introduced accessibility APIs for Carbon and Cocoa in an early version; not sure which one. Unix-based desktop environments got an accessibility API, AT-SPI (thank you Sun), in the early 2000s.
well TIL, I believed accessibility to already be there by the late 80s, in NeXT workstations and the first windows versions but it looks like that was not the case.
