Most Unix systems had it in CDE, 1993. Most also had it in whatever came before.

The first platform to implement multiple desktop display as a hardware feature was Amiga 1000, released in 1985.

The first implementation of virtual desktops for Unix was vtwm in 1990.

https://en.wikipedia.org/wiki/Virtual_desktop

It had been the expected default for pretty much an entire decade. Also X often supported a different size viewport and desktop so the view would scroll. Not sure if anyone really liked using that.