Arguably the November 01981 launch of Silicon Graphics kickstarted GPU interest and OpenGL. You can read Jim Clark's 01982 paper about the Geometry Engine in
https://web.archive.org/web/20170513193926/http://excelsior..... His first key point in the paper was that the chip had a "general instruction set", although what he meant by it was quite different from today's GPUs. IRIS GL started morphing into OpenGL in 01992, and certainly when I went to SIGGRAPH 93 it was full of hardware-accelerated 3-D drawn with OpenGL on Silicon Graphics Hardware. But graphics coprocessors date back to the 60s; Evans & Sutherland was founded in 01968.
I mean, I certainly don't think NVIDIA invented the GPU—that's a clear error in an otherwise pretty decent article—but it was a pretty gradual process.